Merge pull request #12 from go-jet/window-functions

Window functions

README.md

@@ -12,9 +12,12 @@ convert database query result into desired arbitrary object structure.
 Jet currently supports `PostgreSQL`, `MySQL` and `MariaDB`. Future releases will add support for additional databases.
 
 ![jet](https://github.com/go-jet/jet/wiki/image/jet.png)   
-Jet is the easiest and fastest way to write complex SQL queries and map database query result 
+Jet is the easiest and the fastest way to write complex SQL queries and map database query result 
 into complex object composition. __It is not an ORM.__ 
 
+## Motivation
+https://medium.com/@go.jet/jet-5f3667efa0cc
+
 ## Contents
    - [Features](#features)
    - [Getting Started](#getting-started)
@@ -265,7 +268,7 @@ ORDER BY actor.actor_id ASC, film.film_id ASC;
 
 #### Execute query and store result
 
-Well formed SQL is just a first half the job. Lets see how can we make some sense of result set returned executing 
+Well formed SQL is just a first half of the job. Lets see how can we make some sense of result set returned executing 
 above statement. Usually this is the most complex and tedious work, but with Jet it is the easiest.
 
 First we have to create desired structure to store query result set. 
@@ -491,8 +494,8 @@ handleError(err)
 Complete code example can be found at [./examples/quick-start/quick-start.go](./examples/quick-start/quick-start.go)
 
 
-This example represent probably the most common use case.  Detail info about additional features and use cases can be 
+This example represent probably the most common use case.  Detail info about additional statements, features and use cases can be 
-found at project [wiki](https://github.com/go-jet/jet/wiki) page.
+found at project [Wiki](https://github.com/go-jet/jet/wiki) page.
 
 ## Benefits
 
@@ -536,6 +539,8 @@ the bug will be caught at compile time.
 Lets say someone changes the type of `length` column to some non integer type. Build will also fail at the same line
 because integer columns and expressions can be only compered to other integer columns and expressions.
 
+Build will also fail if someone removes `length` column from `film` table, because `Film` field will be omitted from SQL Builder and Model types, next time `jet` generator is run.
+
 Without Jet these bugs will have to be either caught by some test or by manual testing. 
 
 ## Dependencies

internal/jet/clause.go

@@ -135,6 +135,7 @@ func (c *ClauseHaving) Serialize(statementType StatementType, out *SQLBuilder) {
 // ClauseOrderBy struct
 type ClauseOrderBy struct {
 	List        []OrderByClause
+	SkipNewLine bool
 }
 
 // Serialize serializes clause into SQLBuilder
@@ -143,7 +144,9 @@ func (o *ClauseOrderBy) Serialize(statementType StatementType, out *SQLBuilder)
 		return
 	}
 
+	if !o.SkipNewLine {
 		out.NewLine()
+	}
 	out.WriteString("ORDER BY")
 
 	out.IncreaseIdent()
@@ -469,3 +472,37 @@ func (i *ClauseIn) Serialize(statementType StatementType, out *SQLBuilder) {
 	out.WriteString(string(i.LockMode))
 	out.WriteString("MODE")
 }
+
+// WindowDefinition struct
+type WindowDefinition struct {
+	Name   string
+	Window Window
+}
+
+// ClauseWindow struct
+type ClauseWindow struct {
+	Definitions []WindowDefinition
+}
+
+// Serialize serializes clause into SQLBuilder
+func (i *ClauseWindow) Serialize(statementType StatementType, out *SQLBuilder) {
+	if len(i.Definitions) == 0 {
+		return
+	}
+
+	out.NewLine()
+	out.WriteString("WINDOW")
+
+	for i, def := range i.Definitions {
+		if i > 0 {
+			out.WriteString(", ")
+		}
+		out.WriteString(def.Name)
+		out.WriteString("AS")
+		if def.Window == nil {
+			out.WriteString("()")
+			continue
+		}
+		def.Window.serialize(statementType, out)
+	}
+}

internal/jet/func_expression.go

@@ -81,68 +81,154 @@ func LOG(floatExpression FloatExpression) FloatExpression {
 // ----------------- Aggregate functions  -------------------//
 
 // AVG is aggregate function used to calculate avg value from numeric expression
-func AVG(numericExpression NumericExpression) FloatExpression {
+func AVG(numericExpression NumericExpression) floatWindowExpression {
-	return NewFloatFunc("AVG", numericExpression)
+	return NewFloatWindowFunc("AVG", numericExpression)
 }
 
 // BIT_AND is aggregate function used to calculates the bitwise AND of all non-null input values, or null if none.
-func BIT_AND(integerExpression IntegerExpression) IntegerExpression {
+func BIT_AND(integerExpression IntegerExpression) integerWindowExpression {
-	return newIntegerFunc("BIT_AND", integerExpression)
+	return newIntegerWindowFunc("BIT_AND", integerExpression)
 }
 
 // BIT_OR is aggregate function used to calculates the bitwise OR of all non-null input values, or null if none.
-func BIT_OR(integerExpression IntegerExpression) IntegerExpression {
+func BIT_OR(integerExpression IntegerExpression) integerWindowExpression {
-	return newIntegerFunc("BIT_OR", integerExpression)
+	return newIntegerWindowFunc("BIT_OR", integerExpression)
 }
 
 // BOOL_AND is aggregate function. Returns true if all input values are true, otherwise false
-func BOOL_AND(boolExpression BoolExpression) BoolExpression {
+func BOOL_AND(boolExpression BoolExpression) boolWindowExpression {
-	return newBoolFunc("BOOL_AND", boolExpression)
+	return newBoolWindowFunc("BOOL_AND", boolExpression)
 }
 
 // BOOL_OR is aggregate function. Returns true if at least one input value is true, otherwise false
-func BOOL_OR(boolExpression BoolExpression) BoolExpression {
+func BOOL_OR(boolExpression BoolExpression) boolWindowExpression {
-	return newBoolFunc("BOOL_OR", boolExpression)
+	return newBoolWindowFunc("BOOL_OR", boolExpression)
 }
 
 // COUNT is aggregate function. Returns number of input rows for which the value of expression is not null.
-func COUNT(expression Expression) IntegerExpression {
+func COUNT(expression Expression) integerWindowExpression {
-	return newIntegerFunc("COUNT", expression)
+	return newIntegerWindowFunc("COUNT", expression)
 }
 
 // EVERY is aggregate function. Returns true if all input values are true, otherwise false
-func EVERY(boolExpression BoolExpression) BoolExpression {
+func EVERY(boolExpression BoolExpression) boolWindowExpression {
-	return newBoolFunc("EVERY", boolExpression)
+	return newBoolWindowFunc("EVERY", boolExpression)
 }
 
 // MAXf is aggregate function. Returns maximum value of float expression across all input values
-func MAXf(floatExpression FloatExpression) FloatExpression {
+func MAXf(floatExpression FloatExpression) floatWindowExpression {
-	return NewFloatFunc("MAX", floatExpression)
+	return NewFloatWindowFunc("MAX", floatExpression)
 }
 
 // MAXi is aggregate function. Returns maximum value of int expression across all input values
-func MAXi(integerExpression IntegerExpression) IntegerExpression {
+func MAXi(integerExpression IntegerExpression) integerWindowExpression {
-	return newIntegerFunc("MAX", integerExpression)
+	return newIntegerWindowFunc("MAX", integerExpression)
 }
 
 // MINf is aggregate function. Returns minimum value of float expression across all input values
-func MINf(floatExpression FloatExpression) FloatExpression {
+func MINf(floatExpression FloatExpression) floatWindowExpression {
-	return NewFloatFunc("MIN", floatExpression)
+	return NewFloatWindowFunc("MIN", floatExpression)
 }
 
 // MINi is aggregate function. Returns minimum value of int expression across all input values
-func MINi(integerExpression IntegerExpression) IntegerExpression {
+func MINi(integerExpression IntegerExpression) integerWindowExpression {
-	return newIntegerFunc("MIN", integerExpression)
+	return newIntegerWindowFunc("MIN", integerExpression)
 }
 
 // SUMf is aggregate function. Returns sum of expression across all float expressions
-func SUMf(floatExpression FloatExpression) FloatExpression {
+func SUMf(floatExpression FloatExpression) floatWindowExpression {
-	return NewFloatFunc("SUM", floatExpression)
+	return NewFloatWindowFunc("SUM", floatExpression)
 }
 
 // SUMi is aggregate function. Returns sum of expression across all integer expression.
-func SUMi(integerExpression IntegerExpression) IntegerExpression {
+func SUMi(integerExpression IntegerExpression) integerWindowExpression {
-	return newIntegerFunc("SUM", integerExpression)
+	return newIntegerWindowFunc("SUM", integerExpression)
+}
+
+// ----------------- Window functions  -------------------//
+
+// ROW_NUMBER returns number of the current row within its partition, counting from 1
+func ROW_NUMBER() integerWindowExpression {
+	return newIntegerWindowFunc("ROW_NUMBER")
+}
+
+// RANK of the current row with gaps; same as row_number of its first peer
+func RANK() integerWindowExpression {
+	return newIntegerWindowFunc("RANK")
+}
+
+// DENSE_RANK returns rank of the current row without gaps; this function counts peer groups
+func DENSE_RANK() integerWindowExpression {
+	return newIntegerWindowFunc("DENSE_RANK")
+}
+
+// PERCENT_RANK calculates relative rank of the current row: (rank - 1) / (total partition rows - 1)
+func PERCENT_RANK() floatWindowExpression {
+	return NewFloatWindowFunc("PERCENT_RANK")
+}
+
+// CUME_DIST calculates cumulative distribution: (number of partition rows preceding or peer with current row) / total partition rows
+func CUME_DIST() floatWindowExpression {
+	return NewFloatWindowFunc("CUME_DIST")
+}
+
+// NTILE returns integer ranging from 1 to the argument value, dividing the partition as equally as possible
+func NTILE(numOfBuckets int64) integerWindowExpression {
+	return newIntegerWindowFunc("NTILE", FixedLiteral(numOfBuckets))
+}
+
+// LAG returns value evaluated at the row that is offset rows before the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+func LAG(expr Expression, offsetAndDefault ...interface{}) windowExpression {
+	return leadLagImpl("LAG", expr, offsetAndDefault...)
+}
+
+// LEAD returns value evaluated at the row that is offset rows after the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+func LEAD(expr Expression, offsetAndDefault ...interface{}) windowExpression {
+	return leadLagImpl("LEAD", expr, offsetAndDefault...)
+}
+
+// FIRST_VALUE returns value evaluated at the row that is the first row of the window frame
+func FIRST_VALUE(value Expression) windowExpression {
+	return newWindowFunc("FIRST_VALUE", value)
+}
+
+// LAST_VALUE returns value evaluated at the row that is the last row of the window frame
+func LAST_VALUE(value Expression) windowExpression {
+	return newWindowFunc("LAST_VALUE", value)
+}
+
+// NTH_VALUE returns value evaluated at the row that is the nth row of the window frame (counting from 1); null if no such row
+func NTH_VALUE(value Expression, nth int64) windowExpression {
+	return newWindowFunc("NTH_VALUE", value, FixedLiteral(nth))
+}
+
+func leadLagImpl(name string, expr Expression, offsetAndDefault ...interface{}) windowExpression {
+	params := []Expression{expr}
+
+	if len(offsetAndDefault) >= 2 {
+		offset, ok := offsetAndDefault[0].(int)
+		if !ok {
+			panic("jet: LAG offset should be an integer")
+		}
+
+		var defaultValue Expression
+
+		defaultValue, ok = offsetAndDefault[1].(Expression)
+
+		if !ok {
+			defaultValue = literal(offsetAndDefault[1])
+		}
+
+		params = append(params, FixedLiteral(offset), defaultValue)
+	}
+
+	return newWindowFunc(name, params...)
 }
 
 //------------ String functions ------------------//
@@ -349,7 +435,7 @@ func TO_HEX(number IntegerExpression) StringExpression {
 // REGEXP_LIKE Returns 1 if the string expr matches the regular expression specified by the pattern pat, 0 otherwise.
 func REGEXP_LIKE(stringExp StringExpression, pattern StringExpression, matchType ...string) BoolExpression {
 	if len(matchType) > 0 {
-		return newBoolFunc("REGEXP_LIKE", stringExp, pattern, ConstLiteral(matchType[0]))
+		return newBoolFunc("REGEXP_LIKE", stringExp, pattern, FixedLiteral(matchType[0]))
 	}
 
 	return newBoolFunc("REGEXP_LIKE", stringExp, pattern)
@@ -391,7 +477,7 @@ func CURRENT_TIME(precision ...int) TimezExpression {
 	var timezFunc *timezFunc
 
 	if len(precision) > 0 {
-		timezFunc = newTimezFunc("CURRENT_TIME", ConstLiteral(precision[0]))
+		timezFunc = newTimezFunc("CURRENT_TIME", FixedLiteral(precision[0]))
 	} else {
 		timezFunc = newTimezFunc("CURRENT_TIME")
 	}
@@ -406,7 +492,7 @@ func CURRENT_TIMESTAMP(precision ...int) TimestampzExpression {
 	var timestampzFunc *timestampzFunc
 
 	if len(precision) > 0 {
-		timestampzFunc = newTimestampzFunc("CURRENT_TIMESTAMP", ConstLiteral(precision[0]))
+		timestampzFunc = newTimestampzFunc("CURRENT_TIMESTAMP", FixedLiteral(precision[0]))
 	} else {
 		timestampzFunc = newTimestampzFunc("CURRENT_TIMESTAMP")
 	}
@@ -421,7 +507,7 @@ func LOCALTIME(precision ...int) TimeExpression {
 	var timeFunc *timeFunc
 
 	if len(precision) > 0 {
-		timeFunc = newTimeFunc("LOCALTIME", ConstLiteral(precision[0]))
+		timeFunc = newTimeFunc("LOCALTIME", FixedLiteral(precision[0]))
 	} else {
 		timeFunc = newTimeFunc("LOCALTIME")
 	}
@@ -436,7 +522,7 @@ func LOCALTIMESTAMP(precision ...int) TimestampExpression {
 	var timestampFunc *timestampFunc
 
 	if len(precision) > 0 {
-		timestampFunc = NewTimestampFunc("LOCALTIMESTAMP", ConstLiteral(precision[0]))
+		timestampFunc = NewTimestampFunc("LOCALTIMESTAMP", FixedLiteral(precision[0]))
 	} else {
 		timestampFunc = NewTimestampFunc("LOCALTIMESTAMP")
 	}
@@ -504,6 +590,16 @@ func newFunc(name string, expressions []Expression, parent Expression) *funcExpr
 	return funcExp
 }
 
+// NewFloatWindowFunc creates new float function with name and expressions
+func newWindowFunc(name string, expressions ...Expression) windowExpression {
+
+	newFun := newFunc(name, expressions, nil)
+	windowExpr := newWindowExpression(newFun)
+	newFun.expressionInterfaceImpl.Parent = windowExpr
+
+	return windowExpr
+}
+
 func (f *funcExpressionImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
 	if serializeOverride := out.Dialect.FunctionSerializeOverride(f.name); serializeOverride != nil {
 		serializeOverrideFunc := serializeOverride(f.expressions...)
@@ -536,10 +632,23 @@ func newBoolFunc(name string, expressions ...Expression) BoolExpression {
 
 	boolFunc.funcExpressionImpl = *newFunc(name, expressions, boolFunc)
 	boolFunc.boolInterfaceImpl.parent = boolFunc
+	boolFunc.expressionInterfaceImpl.Parent = boolFunc
 
 	return boolFunc
 }
 
+// NewFloatWindowFunc creates new float function with name and expressions
+func newBoolWindowFunc(name string, expressions ...Expression) boolWindowExpression {
+	boolFunc := &boolFunc{}
+
+	boolFunc.funcExpressionImpl = *newFunc(name, expressions, boolFunc)
+	intWindowFunc := newBoolWindowExpression(boolFunc)
+	boolFunc.boolInterfaceImpl.parent = intWindowFunc
+	boolFunc.expressionInterfaceImpl.Parent = intWindowFunc
+
+	return intWindowFunc
+}
+
 type floatFunc struct {
 	funcExpressionImpl
 	floatInterfaceImpl
@@ -555,6 +664,18 @@ func NewFloatFunc(name string, expressions ...Expression) FloatExpression {
 	return floatFunc
 }
 
+// NewFloatWindowFunc creates new float function with name and expressions
+func NewFloatWindowFunc(name string, expressions ...Expression) floatWindowExpression {
+	floatFunc := &floatFunc{}
+
+	floatFunc.funcExpressionImpl = *newFunc(name, expressions, floatFunc)
+	floatWindowFunc := newFloatWindowExpression(floatFunc)
+	floatFunc.floatInterfaceImpl.parent = floatWindowFunc
+	floatFunc.expressionInterfaceImpl.Parent = floatWindowFunc
+
+	return floatWindowFunc
+}
+
 type integerFunc struct {
 	funcExpressionImpl
 	integerInterfaceImpl
@@ -569,6 +690,18 @@ func newIntegerFunc(name string, expressions ...Expression) IntegerExpression {
 	return floatFunc
 }
 
+// NewFloatWindowFunc creates new float function with name and expressions
+func newIntegerWindowFunc(name string, expressions ...Expression) integerWindowExpression {
+	integerFunc := &integerFunc{}
+
+	integerFunc.funcExpressionImpl = *newFunc(name, expressions, integerFunc)
+	intWindowFunc := newIntegerWindowExpression(integerFunc)
+	integerFunc.integerInterfaceImpl.parent = intWindowFunc
+	integerFunc.expressionInterfaceImpl.Parent = intWindowFunc
+
+	return intWindowFunc
+}
+
 type stringFunc struct {
 	funcExpressionImpl
 	stringInterfaceImpl

internal/jet/literal_expression.go

@@ -32,8 +32,8 @@ func literal(value interface{}, optionalConstant ...bool) *literalExpressionImpl
 	return &exp
 }
 
-// ConstLiteral is injected directly to SQL query, and does not appear in argument list.
+// FixedLiteral is injected directly to SQL query, and does not appear in parametrized argument list.
-func ConstLiteral(value interface{}) *literalExpressionImpl {
+func FixedLiteral(value interface{}) *literalExpressionImpl {
 	exp := literal(value)
 	exp.constant = true
 

internal/jet/window_expression.go

@@ -0,0 +1,146 @@
+package jet
+
+type commonWindowImpl struct {
+	expression Expression
+	window     Window
+}
+
+func (w *commonWindowImpl) over(window ...Window) {
+	if len(window) > 0 {
+		w.window = window[0]
+	} else {
+		w.window = newWindowImpl(nil)
+	}
+}
+
+func (w *commonWindowImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	w.expression.serialize(statement, out)
+	if w.window != nil {
+		out.WriteString("OVER")
+		w.window.serialize(statement, out)
+	}
+}
+
+// --------------------------------------
+
+type windowExpression interface {
+	Expression
+	OVER(window ...Window) Expression
+}
+
+func newWindowExpression(Exp Expression) windowExpression {
+	newExp := &windowExpressionImpl{
+		Expression: Exp,
+	}
+
+	newExp.commonWindowImpl.expression = Exp
+
+	return newExp
+}
+
+type windowExpressionImpl struct {
+	Expression
+	commonWindowImpl
+}
+
+func (f *windowExpressionImpl) OVER(window ...Window) Expression {
+	f.commonWindowImpl.over(window...)
+	return f
+}
+
+func (f *windowExpressionImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	f.commonWindowImpl.serialize(statement, out)
+}
+
+// -----------------------------------------------------
+
+type floatWindowExpression interface {
+	FloatExpression
+	OVER(window ...Window) FloatExpression
+}
+
+func newFloatWindowExpression(floatExp FloatExpression) floatWindowExpression {
+	newExp := &floatWindowExpressionImpl{
+		FloatExpression: floatExp,
+	}
+
+	newExp.commonWindowImpl.expression = floatExp
+
+	return newExp
+}
+
+type floatWindowExpressionImpl struct {
+	FloatExpression
+	commonWindowImpl
+}
+
+func (f *floatWindowExpressionImpl) OVER(window ...Window) FloatExpression {
+	f.commonWindowImpl.over(window...)
+	return f
+}
+
+func (f *floatWindowExpressionImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	f.commonWindowImpl.serialize(statement, out)
+}
+
+// ------------------------------------------------
+
+type integerWindowExpression interface {
+	IntegerExpression
+	OVER(window ...Window) IntegerExpression
+}
+
+func newIntegerWindowExpression(intExp IntegerExpression) integerWindowExpression {
+	newExp := &integerWindowExpressionImpl{
+		IntegerExpression: intExp,
+	}
+
+	newExp.commonWindowImpl.expression = intExp
+
+	return newExp
+}
+
+type integerWindowExpressionImpl struct {
+	IntegerExpression
+	commonWindowImpl
+}
+
+func (f *integerWindowExpressionImpl) OVER(window ...Window) IntegerExpression {
+	f.commonWindowImpl.over(window...)
+	return f
+}
+
+func (f *integerWindowExpressionImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	f.commonWindowImpl.serialize(statement, out)
+}
+
+// ------------------------------------------------
+
+type boolWindowExpression interface {
+	BoolExpression
+	OVER(window ...Window) BoolExpression
+}
+
+func newBoolWindowExpression(boolExp BoolExpression) boolWindowExpression {
+	newExp := &boolWindowExpressionImpl{
+		BoolExpression: boolExp,
+	}
+
+	newExp.commonWindowImpl.expression = boolExp
+
+	return newExp
+}
+
+type boolWindowExpressionImpl struct {
+	BoolExpression
+	commonWindowImpl
+}
+
+func (f *boolWindowExpressionImpl) OVER(window ...Window) BoolExpression {
+	f.commonWindowImpl.over(window...)
+	return f
+}
+
+func (f *boolWindowExpressionImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	f.commonWindowImpl.serialize(statement, out)
+}

internal/jet/window_func.go

@@ -0,0 +1,186 @@
+package jet
+
+// Window interface
+type Window interface {
+	Serializer
+	ORDER_BY(expr ...OrderByClause) Window
+	ROWS(start FrameExtent, end ...FrameExtent) Window
+	RANGE(start FrameExtent, end ...FrameExtent) Window
+	GROUPS(start FrameExtent, end ...FrameExtent) Window
+}
+
+type windowImpl struct {
+	partitionBy []Expression
+	orderBy     ClauseOrderBy
+	frameUnits  string
+	start, end  FrameExtent
+
+	parent Window
+}
+
+func newWindowImpl(parent Window) *windowImpl {
+	newWindow := &windowImpl{}
+	if parent == nil {
+		newWindow.parent = newWindow
+	} else {
+		newWindow.parent = parent
+	}
+
+	return newWindow
+}
+
+func (w *windowImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	if !contains(options, noWrap) {
+		out.WriteByte('(')
+	}
+
+	if w.partitionBy != nil {
+		out.WriteString("PARTITION BY")
+
+		serializeExpressionList(statement, w.partitionBy, ", ", out)
+	}
+	w.orderBy.SkipNewLine = true
+	w.orderBy.Serialize(statement, out)
+
+	if w.frameUnits != "" {
+		out.WriteString(w.frameUnits)
+
+		if w.end == nil {
+			w.start.serialize(statement, out)
+		} else {
+			out.WriteString("BETWEEN")
+			w.start.serialize(statement, out)
+			out.WriteString("AND")
+			w.end.serialize(statement, out)
+		}
+	}
+
+	if !contains(options, noWrap) {
+		out.WriteByte(')')
+	}
+}
+
+func (w *windowImpl) ORDER_BY(exprs ...OrderByClause) Window {
+	w.orderBy.List = exprs
+	return w.parent
+}
+
+func (w *windowImpl) ROWS(start FrameExtent, end ...FrameExtent) Window {
+	w.frameUnits = "ROWS"
+	w.setFrameRange(start, end...)
+	return w.parent
+}
+
+func (w *windowImpl) RANGE(start FrameExtent, end ...FrameExtent) Window {
+	w.frameUnits = "RANGE"
+	w.setFrameRange(start, end...)
+	return w.parent
+}
+
+func (w *windowImpl) GROUPS(start FrameExtent, end ...FrameExtent) Window {
+	w.frameUnits = "GROUPS"
+	w.setFrameRange(start, end...)
+	return w.parent
+}
+
+func (w *windowImpl) setFrameRange(start FrameExtent, end ...FrameExtent) {
+	w.start = start
+	if len(end) > 0 {
+		w.end = end[0]
+	}
+}
+
+// PARTITION_BY window function constructor
+func PARTITION_BY(exp Expression, exprs ...Expression) Window {
+	funImpl := newWindowImpl(nil)
+	funImpl.partitionBy = append([]Expression{exp}, exprs...)
+	return funImpl
+}
+
+// ORDER_BY window function constructor
+func ORDER_BY(expr ...OrderByClause) Window {
+	funImpl := newWindowImpl(nil)
+	funImpl.orderBy.List = expr
+	return funImpl
+}
+
+// -----------------------------------------------
+
+// FrameExtent interface
+type FrameExtent interface {
+	Serializer
+	isFrameExtent()
+}
+
+// PRECEDING window frame clause
+func PRECEDING(offset Serializer) FrameExtent {
+	return &frameExtentImpl{
+		preceding: true,
+		offset:    offset,
+	}
+}
+
+// FOLLOWING window frame clause
+func FOLLOWING(offset Serializer) FrameExtent {
+	return &frameExtentImpl{
+		preceding: false,
+		offset:    offset,
+	}
+}
+
+type frameExtentImpl struct {
+	preceding bool
+	offset    Serializer
+}
+
+func (f *frameExtentImpl) isFrameExtent() {}
+
+func (f *frameExtentImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	if f == nil {
+		return
+	}
+	f.offset.serialize(statement, out)
+
+	if f.preceding {
+		out.WriteString("PRECEDING")
+	} else {
+		out.WriteString("FOLLOWING")
+	}
+}
+
+// -----------------------------------------------
+
+// Window function keywords
+var (
+	UNBOUNDED   = keywordClause("UNBOUNDED")
+	CURRENT_ROW = frameExtentKeyword{"CURRENT ROW"}
+)
+
+type frameExtentKeyword struct {
+	keywordClause
+}
+
+func (f frameExtentKeyword) isFrameExtent() {}
+
+// -----------------------------------------------
+
+// WindowName is used to specify window reference from WINDOW clause
+func WindowName(name string) Window {
+	newWindow := &windowName{name: name}
+	newWindow.parent = newWindow
+	return newWindow
+}
+
+type windowName struct {
+	windowImpl
+	name string
+}
+
+func (w windowName) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
+	out.WriteByte('(')
+
+	out.WriteString(w.name)
+	w.windowImpl.serialize(statement, out, noWrap)
+
+	out.WriteByte(')')
+}

internal/jet/window_func_test.go

@@ -0,0 +1,21 @@
+package jet
+
+import "testing"
+
+func TestFrameExtent(t *testing.T) {
+	assertClauseSerialize(t, PRECEDING(Int(2)), "$1 PRECEDING", int64(2))
+	assertClauseSerialize(t, FOLLOWING(Int(4)), "$1 FOLLOWING", int64(4))
+}
+
+func TestWindowFunctions(t *testing.T) {
+	assertClauseSerialize(t, PARTITION_BY(table1Col1), "(PARTITION BY table1.col1)")
+	assertClauseSerialize(t, PARTITION_BY(table1Col3).ORDER_BY(table1Col1), "(PARTITION BY table1.col3 ORDER BY table1.col1)")
+	assertClauseSerialize(t, ORDER_BY(table1Col1), "(ORDER BY table1.col1)")
+	assertClauseSerialize(t, ORDER_BY(table1Col1).ROWS(PRECEDING(Int(1))), "(ORDER BY table1.col1 ROWS $1 PRECEDING)", int64(1))
+	assertClauseSerialize(t, ORDER_BY(table1Col1).ROWS(PRECEDING(Int(1)), FOLLOWING(Int(33))),
+		"(ORDER BY table1.col1 ROWS BETWEEN $1 PRECEDING AND $2 FOLLOWING)", int64(1), int64(33))
+	assertClauseSerialize(t, ORDER_BY(table1Col1).RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED)),
+		"(ORDER BY table1.col1 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)")
+	assertClauseSerialize(t, ORDER_BY(table1Col1).RANGE(PRECEDING(UNBOUNDED), CURRENT_ROW),
+		"(ORDER BY table1.col1 RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)")
+}

mysql/functions.go

@@ -85,6 +85,47 @@ var SUMi = jet.SUMi
 // SUMf is aggregate function. Returns sum of float expression.
 var SUMf = jet.SUMf
 
+// -------------------- Window functions -----------------------//
+
+// ROW_NUMBER returns number of the current row within its partition, counting from 1
+var ROW_NUMBER = jet.ROW_NUMBER
+
+// RANK of the current row with gaps; same as row_number of its first peer
+var RANK = jet.RANK
+
+// DENSE_RANK returns rank of the current row without gaps; this function counts peer groups
+var DENSE_RANK = jet.DENSE_RANK
+
+// PERCENT_RANK calculates relative rank of the current row: (rank - 1) / (total partition rows - 1)
+var PERCENT_RANK = jet.PERCENT_RANK
+
+// CUME_DIST calculates cumulative distribution: (number of partition rows preceding or peer with current row) / total partition rows
+var CUME_DIST = jet.CUME_DIST
+
+// NTILE returns integer ranging from 1 to the argument value, dividing the partition as equally as possible
+var NTILE = jet.NTILE
+
+// LAG returns value evaluated at the row that is offset rows before the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+var LAG = jet.LAG
+
+// LEAD returns value evaluated at the row that is offset rows after the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+var LEAD = jet.LEAD
+
+// FIRST_VALUE returns value evaluated at the row that is the first row of the window frame
+var FIRST_VALUE = jet.FIRST_VALUE
+
+// LAST_VALUE returns value evaluated at the row that is the last row of the window frame
+var LAST_VALUE = jet.LAST_VALUE
+
+// NTH_VALUE returns value evaluated at the row that is the nth row of the window frame (counting from 1); null if no such row
+var NTH_VALUE = jet.NTH_VALUE
+
 //--------------------- String functions ------------------//
 
 // BIT_LENGTH returns number of bits in string expression
@@ -181,7 +222,7 @@ func CURRENT_TIMESTAMP(precision ...int) TimestampExpression {
 // NOW returns current datetime
 func NOW(fsp ...int) DateTimeExpression {
 	if len(fsp) > 0 {
-		return jet.NewTimestampFunc("NOW", jet.ConstLiteral(int64(fsp[0])))
+		return jet.NewTimestampFunc("NOW", jet.FixedLiteral(int64(fsp[0])))
 	}
 	return jet.NewTimestampFunc("NOW")
 }

mysql/select_statement.go

@@ -1,6 +1,8 @@
 package mysql
 
-import "github.com/go-jet/jet/internal/jet"
+import (
+	"github.com/go-jet/jet/internal/jet"
+)
 
 // RowLock is interface for SELECT statement row lock types
 type RowLock = jet.RowLock
@@ -11,6 +13,27 @@ var (
 	SHARE  = jet.NewRowLock("SHARE")
 )
 
+// Window function clauses
+var (
+	PARTITION_BY = jet.PARTITION_BY
+	ORDER_BY     = jet.ORDER_BY
+	UNBOUNDED    = jet.UNBOUNDED
+	CURRENT_ROW  = jet.CURRENT_ROW
+)
+
+// PRECEDING window frame clause
+func PRECEDING(offset interface{}) jet.FrameExtent {
+	return jet.PRECEDING(toJetFrameOffset(offset))
+}
+
+// FOLLOWING window frame clause
+func FOLLOWING(offset interface{}) jet.FrameExtent {
+	return jet.FOLLOWING(toJetFrameOffset(offset))
+}
+
+// Window is used to specify window reference from WINDOW clause
+var Window = jet.WindowName
+
 // SelectStatement is interface for MySQL SELECT statement
 type SelectStatement interface {
 	Statement
@@ -22,6 +45,7 @@ type SelectStatement interface {
 	WHERE(expression BoolExpression) SelectStatement
 	GROUP_BY(groupByClauses ...jet.GroupByClause) SelectStatement
 	HAVING(boolExpression BoolExpression) SelectStatement
+	WINDOW(name string) windowExpand
 	ORDER_BY(orderByClauses ...jet.OrderByClause) SelectStatement
 	LIMIT(limit int64) SelectStatement
 	OFFSET(offset int64) SelectStatement
@@ -42,7 +66,7 @@ func SELECT(projection Projection, projections ...Projection) SelectStatement {
 func newSelectStatement(table ReadableTable, projections []Projection) SelectStatement {
 	newSelect := &selectStatementImpl{}
 	newSelect.ExpressionStatement = jet.NewExpressionStatementImpl(Dialect, jet.SelectStatementType, newSelect, &newSelect.Select,
-		&newSelect.From, &newSelect.Where, &newSelect.GroupBy, &newSelect.Having, &newSelect.OrderBy,
+		&newSelect.From, &newSelect.Where, &newSelect.GroupBy, &newSelect.Having, &newSelect.Window, &newSelect.OrderBy,
 		&newSelect.Limit, &newSelect.Offset, &newSelect.For, &newSelect.ShareLock)
 
 	newSelect.Select.Projections = toJetProjectionList(projections)
@@ -66,6 +90,7 @@ type selectStatementImpl struct {
 	Where     jet.ClauseWhere
 	GroupBy   jet.ClauseGroupBy
 	Having    jet.ClauseHaving
+	Window    jet.ClauseWindow
 	OrderBy   jet.ClauseOrderBy
 	Limit     jet.ClauseLimit
 	Offset    jet.ClauseOffset
@@ -98,6 +123,11 @@ func (s *selectStatementImpl) HAVING(boolExpression BoolExpression) SelectStatem
 	return s
 }
 
+func (s *selectStatementImpl) WINDOW(name string) windowExpand {
+	s.Window.Definitions = append(s.Window.Definitions, jet.WindowDefinition{Name: name})
+	return windowExpand{selectStatement: s}
+}
+
 func (s *selectStatementImpl) ORDER_BY(orderByClauses ...jet.OrderByClause) SelectStatement {
 	s.OrderBy.List = orderByClauses
 	return s
@@ -126,3 +156,31 @@ func (s *selectStatementImpl) LOCK_IN_SHARE_MODE() SelectStatement {
 func (s *selectStatementImpl) AsTable(alias string) SelectTable {
 	return newSelectTable(s, alias)
 }
+
+//-----------------------------------------------------
+
+type windowExpand struct {
+	selectStatement *selectStatementImpl
+}
+
+func (w windowExpand) AS(window ...jet.Window) SelectStatement {
+	if len(window) == 0 {
+		return w.selectStatement
+	}
+	windowsDefinition := w.selectStatement.Window.Definitions
+	windowsDefinition[len(windowsDefinition)-1].Window = window[0]
+	return w.selectStatement
+}
+
+func toJetFrameOffset(offset interface{}) jet.Serializer {
+	if offset == UNBOUNDED {
+		return jet.UNBOUNDED
+	}
+
+	// check for interval expression
+	//if exp, ok := offset.(Expression); ok {
+	//	return exp
+	//}
+
+	return jet.FixedLiteral(offset)
+}

postgres/functions.go

@@ -87,6 +87,47 @@ var SUMf = jet.SUMf
 // SUMi is aggregate function. Returns sum of expression across all integer expression.
 var SUMi = jet.SUMi
 
+// -------------------- Window functions -----------------------//
+
+// ROW_NUMBER returns number of the current row within its partition, counting from 1
+var ROW_NUMBER = jet.ROW_NUMBER
+
+// RANK of the current row with gaps; same as row_number of its first peer
+var RANK = jet.RANK
+
+// DENSE_RANK returns rank of the current row without gaps; this function counts peer groups
+var DENSE_RANK = jet.DENSE_RANK
+
+// PERCENT_RANK calculates relative rank of the current row: (rank - 1) / (total partition rows - 1)
+var PERCENT_RANK = jet.PERCENT_RANK
+
+// CUME_DIST calculates cumulative distribution: (number of partition rows preceding or peer with current row) / total partition rows
+var CUME_DIST = jet.CUME_DIST
+
+// NTILE returns integer ranging from 1 to the argument value, dividing the partition as equally as possible
+var NTILE = jet.NTILE
+
+// LAG returns value evaluated at the row that is offset rows before the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+var LAG = jet.LAG
+
+// LEAD returns value evaluated at the row that is offset rows after the current row within the partition;
+// if there is no such row, instead return default (which must be of the same type as value).
+// Both offset and default are evaluated with respect to the current row.
+// If omitted, offset defaults to 1 and default to null
+var LEAD = jet.LEAD
+
+// FIRST_VALUE returns value evaluated at the row that is the first row of the window frame
+var FIRST_VALUE = jet.FIRST_VALUE
+
+// LAST_VALUE returns value evaluated at the row that is the last row of the window frame
+var LAST_VALUE = jet.LAST_VALUE
+
+// NTH_VALUE returns value evaluated at the row that is the nth row of the window frame (counting from 1); null if no such row
+var NTH_VALUE = jet.NTH_VALUE
+
 //--------------------- String functions ------------------//
 
 // BIT_LENGTH returns number of bits in string expression

postgres/select_statement.go

@@ -1,6 +1,9 @@
 package postgres
 
-import "github.com/go-jet/jet/internal/jet"
+import (
+	"github.com/go-jet/jet/internal/jet"
+	"math"
+)
 
 // RowLock is interface for SELECT statement row lock types
 type RowLock = jet.RowLock
@@ -13,6 +16,27 @@ var (
 	KEY_SHARE     = jet.NewRowLock("KEY SHARE")
 )
 
+// Window function clauses
+var (
+	PARTITION_BY = jet.PARTITION_BY
+	ORDER_BY     = jet.ORDER_BY
+	UNBOUNDED    = int64(math.MaxInt64)
+	CURRENT_ROW  = jet.CURRENT_ROW
+)
+
+// PRECEDING window frame clause
+func PRECEDING(offset int64) jet.FrameExtent {
+	return jet.PRECEDING(toJetFrameOffset(offset))
+}
+
+// FOLLOWING window frame clause
+func FOLLOWING(offset int64) jet.FrameExtent {
+	return jet.FOLLOWING(toJetFrameOffset(offset))
+}
+
+// Window definition reference
+var Window = jet.WindowName
+
 // SelectStatement is interface for PostgreSQL SELECT statement
 type SelectStatement interface {
 	Statement
@@ -24,6 +48,7 @@ type SelectStatement interface {
 	WHERE(expression BoolExpression) SelectStatement
 	GROUP_BY(groupByClauses ...jet.GroupByClause) SelectStatement
 	HAVING(boolExpression BoolExpression) SelectStatement
+	WINDOW(name string) windowExpand
 	ORDER_BY(orderByClauses ...jet.OrderByClause) SelectStatement
 	LIMIT(limit int64) SelectStatement
 	OFFSET(offset int64) SelectStatement
@@ -47,15 +72,9 @@ func SELECT(projection Projection, projections ...Projection) SelectStatement {
 func newSelectStatement(table ReadableTable, projections []Projection) SelectStatement {
 	newSelect := &selectStatementImpl{}
 	newSelect.ExpressionStatement = jet.NewExpressionStatementImpl(Dialect, jet.SelectStatementType, newSelect, &newSelect.Select,
-		&newSelect.From, &newSelect.Where, &newSelect.GroupBy, &newSelect.Having, &newSelect.OrderBy,
+		&newSelect.From, &newSelect.Where, &newSelect.GroupBy, &newSelect.Having, &newSelect.Window, &newSelect.OrderBy,
 		&newSelect.Limit, &newSelect.Offset, &newSelect.For)
 
-	//	statementImpl = jet.NewStatementImpl(Dialect, jet.SelectStatementType, newSelect, &newSelect.Select,
-	//	&newSelect.From, &newSelect.Where, &newSelect.GroupBy, &newSelect.Having, &newSelect.OrderBy,
-	//	&newSelect.Limit, &newSelect.Offset, &newSelect.For)
-	//
-	//newSelect.expressionStatementImpl.expressionInterfaceImpl.Parent = newSelect
-
 	newSelect.Select.Projections = toJetProjectionList(projections)
 	newSelect.From.Table = table
 	newSelect.Limit.Count = -1
@@ -75,6 +94,7 @@ type selectStatementImpl struct {
 	Where   jet.ClauseWhere
 	GroupBy jet.ClauseGroupBy
 	Having  jet.ClauseHaving
+	Window  jet.ClauseWindow
 	OrderBy jet.ClauseOrderBy
 	Limit   jet.ClauseLimit
 	Offset  jet.ClauseOffset
@@ -106,6 +126,11 @@ func (s *selectStatementImpl) HAVING(boolExpression BoolExpression) SelectStatem
 	return s
 }
 
+func (s *selectStatementImpl) WINDOW(name string) windowExpand {
+	s.Window.Definitions = append(s.Window.Definitions, jet.WindowDefinition{Name: name})
+	return windowExpand{selectStatement: s}
+}
+
 func (s *selectStatementImpl) ORDER_BY(orderByClauses ...jet.OrderByClause) SelectStatement {
 	s.OrderBy.List = orderByClauses
 	return s
@@ -129,3 +154,25 @@ func (s *selectStatementImpl) FOR(lock RowLock) SelectStatement {
 func (s *selectStatementImpl) AsTable(alias string) SelectTable {
 	return newSelectTable(s, alias)
 }
+
+//-----------------------------------------------------
+
+type windowExpand struct {
+	selectStatement *selectStatementImpl
+}
+
+func (w windowExpand) AS(window ...jet.Window) SelectStatement {
+	if len(window) == 0 {
+		return w.selectStatement
+	}
+	windowsDefinition := w.selectStatement.Window.Definitions
+	windowsDefinition[len(windowsDefinition)-1].Window = window[0]
+	return w.selectStatement
+}
+
+func toJetFrameOffset(offset int64) jet.Serializer {
+	if offset == UNBOUNDED {
+		return jet.UNBOUNDED
+	}
+	return jet.FixedLiteral(offset)
+}

tests/mysql/select_test.go

@@ -1,6 +1,7 @@
 package mysql
 
 import (
+	"fmt"
 	"github.com/go-jet/jet/internal/testutils"
 	. "github.com/go-jet/jet/mysql"
 	"github.com/go-jet/jet/tests/.gentestdata/mysql/dvds/enum"
@@ -527,3 +528,115 @@ LOCK IN SHARE MODE;
 	err := query.Query(db, &struct{}{})
 	assert.NilError(t, err)
 }
+
+func TestWindowFunction(t *testing.T) {
+
+	if sourceIsMariaDB() {
+		return
+	}
+
+	var expectedSQL = `
+SELECT AVG(payment.amount) OVER (),
+     AVG(payment.amount) OVER (PARTITION BY payment.customer_id),
+     MAX(payment.amount) OVER (ORDER BY payment.payment_date DESC),
+     MIN(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     SUM(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC ROWS BETWEEN 1 PRECEDING AND 6 FOLLOWING),
+     SUM(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+     MAX(payment.customer_id) OVER (ORDER BY payment.payment_date DESC ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING),
+     MIN(payment.customer_id) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     SUM(payment.customer_id) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     ROW_NUMBER() OVER (ORDER BY payment.payment_date),
+     RANK() OVER (ORDER BY payment.payment_date),
+     DENSE_RANK() OVER (ORDER BY payment.payment_date),
+     CUME_DIST() OVER (ORDER BY payment.payment_date),
+     NTILE(11) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount, 2, payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount, 2, ?) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount, 2, payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount, 2, ?) OVER (ORDER BY payment.payment_date),
+     FIRST_VALUE(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAST_VALUE(payment.amount) OVER (ORDER BY payment.payment_date),
+     NTH_VALUE(payment.amount, 3) OVER (ORDER BY payment.payment_date)
+FROM dvds.payment
+WHERE payment.payment_id < ?
+GROUP BY payment.amount, payment.customer_id, payment.payment_date;
+`
+	query := Payment.
+		SELECT(
+			AVG(Payment.Amount).OVER(),
+			AVG(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID)),
+			MAXf(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate.DESC())),
+			MINf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			SUMf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).
+				ORDER_BY(Payment.PaymentDate.DESC()).ROWS(PRECEDING(1), FOLLOWING(6))),
+			SUMf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).
+				ORDER_BY(Payment.PaymentDate.DESC()).RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED))),
+			MAXi(Payment.CustomerID).OVER(ORDER_BY(Payment.PaymentDate.DESC()).ROWS(CURRENT_ROW, FOLLOWING(UNBOUNDED))),
+			MINi(Payment.CustomerID).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			SUMi(Payment.CustomerID).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			ROW_NUMBER().OVER(ORDER_BY(Payment.PaymentDate)),
+			RANK().OVER(ORDER_BY(Payment.PaymentDate)),
+			DENSE_RANK().OVER(ORDER_BY(Payment.PaymentDate)),
+			CUME_DIST().OVER(ORDER_BY(Payment.PaymentDate)),
+			NTILE(11).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2, Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2, 100).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2, Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2, 100).OVER(ORDER_BY(Payment.PaymentDate)),
+			FIRST_VALUE(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAST_VALUE(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			NTH_VALUE(Payment.Amount, 3).OVER(ORDER_BY(Payment.PaymentDate)),
+		).GROUP_BY(Payment.Amount, Payment.CustomerID, Payment.PaymentDate).
+		WHERE(Payment.PaymentID.LT(Int(10)))
+
+	fmt.Println(query.Sql())
+
+	testutils.AssertStatementSql(t, query, expectedSQL, 100, 100, int64(10))
+
+	err := query.Query(db, &struct{}{})
+	assert.NilError(t, err)
+}
+
+func TestWindowClause(t *testing.T) {
+	var expectedSQL = `
+SELECT AVG(payment.amount) OVER (),
+     AVG(payment.amount) OVER (w1),
+     AVG(payment.amount) OVER (w2 ORDER BY payment.customer_id RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+     AVG(payment.amount) OVER (w3 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
+FROM dvds.payment
+WHERE payment.payment_id < ?
+WINDOW w1 AS (PARTITION BY payment.payment_date), w2 AS (w1), w3 AS (w2 ORDER BY payment.customer_id)
+ORDER BY payment.customer_id;
+`
+	query := Payment.SELECT(
+		AVG(Payment.Amount).OVER(),
+		AVG(Payment.Amount).OVER(Window("w1")),
+		AVG(Payment.Amount).OVER(
+			Window("w2").
+				ORDER_BY(Payment.CustomerID).
+				RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED)),
+		),
+		AVG(Payment.Amount).OVER(Window("w3").RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED))),
+	).
+		WHERE(Payment.PaymentID.LT(Int(10))).
+		WINDOW("w1").AS(PARTITION_BY(Payment.PaymentDate)).
+		WINDOW("w2").AS(Window("w1")).
+		WINDOW("w3").AS(Window("w2").ORDER_BY(Payment.CustomerID)).
+		ORDER_BY(Payment.CustomerID)
+
+	fmt.Println(query.Sql())
+
+	testutils.AssertStatementSql(t, query, expectedSQL, int64(10))
+
+	err := query.Query(db, &struct{}{})
+
+	assert.NilError(t, err)
+}

tests/postgres/select_test.go

@@ -1615,3 +1615,110 @@ SELECT true,
 	err := query.Query(db, &struct{}{})
 	assert.NilError(t, err)
 }
+
+func TestWindowFunction(t *testing.T) {
+	var expectedSQL = `
+SELECT AVG(payment.amount) OVER (),
+     AVG(payment.amount) OVER (PARTITION BY payment.customer_id),
+     MAX(payment.amount) OVER (ORDER BY payment.payment_date DESC),
+     MIN(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     SUM(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC ROWS BETWEEN 1 PRECEDING AND 6 FOLLOWING),
+     SUM(payment.amount) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+     MAX(payment.customer_id) OVER (ORDER BY payment.payment_date DESC ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING),
+     MIN(payment.customer_id) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     SUM(payment.customer_id) OVER (PARTITION BY payment.customer_id ORDER BY payment.payment_date DESC),
+     ROW_NUMBER() OVER (ORDER BY payment.payment_date),
+     RANK() OVER (ORDER BY payment.payment_date),
+     DENSE_RANK() OVER (ORDER BY payment.payment_date),
+     CUME_DIST() OVER (ORDER BY payment.payment_date),
+     NTILE(11) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount, 2, payment.amount) OVER (ORDER BY payment.payment_date),
+     LAG(payment.amount, 2, $1) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount, 2, payment.amount) OVER (ORDER BY payment.payment_date),
+     LEAD(payment.amount, 2, $2) OVER (ORDER BY payment.payment_date),
+     FIRST_VALUE(payment.amount) OVER (ORDER BY payment.payment_date),
+     LAST_VALUE(payment.amount) OVER (ORDER BY payment.payment_date),
+     NTH_VALUE(payment.amount, 3) OVER (ORDER BY payment.payment_date)
+FROM dvds.payment
+WHERE payment.payment_id < $3
+GROUP BY payment.amount, payment.customer_id, payment.payment_date;
+`
+	query := Payment.
+		SELECT(
+			AVG(Payment.Amount).OVER(),
+			AVG(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID)),
+			MAXf(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate.DESC())),
+			MINf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			SUMf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).
+				ORDER_BY(Payment.PaymentDate.DESC()).ROWS(PRECEDING(1), FOLLOWING(6))),
+			SUMf(Payment.Amount).OVER(PARTITION_BY(Payment.CustomerID).
+				ORDER_BY(Payment.PaymentDate.DESC()).RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED))),
+			MAXi(Payment.CustomerID).OVER(ORDER_BY(Payment.PaymentDate.DESC()).ROWS(CURRENT_ROW, FOLLOWING(UNBOUNDED))),
+			MINi(Payment.CustomerID).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			SUMi(Payment.CustomerID).OVER(PARTITION_BY(Payment.CustomerID).ORDER_BY(Payment.PaymentDate.DESC())),
+			ROW_NUMBER().OVER(ORDER_BY(Payment.PaymentDate)),
+			RANK().OVER(ORDER_BY(Payment.PaymentDate)),
+			DENSE_RANK().OVER(ORDER_BY(Payment.PaymentDate)),
+			CUME_DIST().OVER(ORDER_BY(Payment.PaymentDate)),
+			NTILE(11).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2, Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAG(Payment.Amount, 2, 100).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2, Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LEAD(Payment.Amount, 2, 100).OVER(ORDER_BY(Payment.PaymentDate)),
+			FIRST_VALUE(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			LAST_VALUE(Payment.Amount).OVER(ORDER_BY(Payment.PaymentDate)),
+			NTH_VALUE(Payment.Amount, 3).OVER(ORDER_BY(Payment.PaymentDate)),
+		).GROUP_BY(Payment.Amount, Payment.CustomerID, Payment.PaymentDate).
+		WHERE(Payment.PaymentID.LT(Int(10)))
+
+	fmt.Println(query.Sql())
+
+	testutils.AssertStatementSql(t, query, expectedSQL, 100, 100, int64(10))
+
+	err := query.Query(db, &struct{}{})
+	assert.NilError(t, err)
+}
+
+func TestWindowClause(t *testing.T) {
+	var expectedSQL = `
+SELECT AVG(payment.amount) OVER (),
+     AVG(payment.amount) OVER (w1),
+     AVG(payment.amount) OVER (w2 ORDER BY payment.customer_id RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+     AVG(payment.amount) OVER (w3 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
+FROM dvds.payment
+WHERE payment.payment_id < $1
+WINDOW w1 AS (PARTITION BY payment.payment_date), w2 AS (w1), w3 AS (w2 ORDER BY payment.customer_id)
+ORDER BY payment.customer_id;
+`
+	query := Payment.SELECT(
+		AVG(Payment.Amount).OVER(),
+		AVG(Payment.Amount).OVER(Window("w1")),
+		AVG(Payment.Amount).OVER(
+			Window("w2").
+				ORDER_BY(Payment.CustomerID).
+				RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED)),
+		),
+		AVG(Payment.Amount).OVER(Window("w3").RANGE(PRECEDING(UNBOUNDED), FOLLOWING(UNBOUNDED))),
+	).
+		WHERE(Payment.PaymentID.LT(Int(10))).
+		WINDOW("w1").AS(PARTITION_BY(Payment.PaymentDate)).
+		WINDOW("w2").AS(Window("w1")).
+		WINDOW("w3").AS(Window("w2").ORDER_BY(Payment.CustomerID)).
+		ORDER_BY(Payment.CustomerID)
+
+	fmt.Println(query.Sql())
+
+	testutils.AssertStatementSql(t, query, expectedSQL, int64(10))
+
+	err := query.Query(db, &struct{}{})
+
+	assert.NilError(t, err)
+}