diff --git a/execution/execution.go b/execution/execution.go
index e29f46a..363b0f4 100644
--- a/execution/execution.go
+++ b/execution/execution.go
@@ -271,7 +271,6 @@ func mapRowToStruct(scanContext *scanContext, groupKey string, structPtrValue re
 
 				if err != nil {
 					panic("jet: " + err.Error() + ", " + fieldToString(&field) + " of type " + structType.String())
-					return
 				}
 				updated = true
 			} else {
diff --git a/internal/jet/clause.go b/internal/jet/clause.go
index b64dc0e..95283a1 100644
--- a/internal/jet/clause.go
+++ b/internal/jet/clause.go
@@ -11,7 +11,7 @@ type Clause interface {
 type ClauseWithProjections interface {
 	Clause
 
-	projections() []Projection
+	projections() ProjectionList
 }
 
 type ClauseSelect struct {
@@ -19,7 +19,7 @@ type ClauseSelect struct {
 	Projections []Projection
 }
 
-func (s *ClauseSelect) projections() []Projection {
+func (s *ClauseSelect) projections() ProjectionList {
 	return s.Projections
 }
 
@@ -172,7 +172,7 @@ type ClauseSetStmtOperator struct {
 	Offset   ClauseOffset
 }
 
-func (s *ClauseSetStmtOperator) projections() []Projection {
+func (s *ClauseSetStmtOperator) projections() ProjectionList {
 	if len(s.Selects) > 0 {
 		return s.Selects[0].projections()
 	}
diff --git a/internal/jet/func_expression.go b/internal/jet/func_expression.go
index 45ee0f5..2e6e9dd 100644
--- a/internal/jet/func_expression.go
+++ b/internal/jet/func_expression.go
@@ -17,10 +17,12 @@ func ABSi(integerExpression IntegerExpression) IntegerExpression {
 	return newIntegerFunc("ABS", integerExpression)
 }
 
+// POW calculates power of base with exponent
 func POW(base, exponent NumericExpression) FloatExpression {
 	return NewFloatFunc("POW", base, exponent)
 }
 
+// POWER calculates power of base with exponent
 func POWER(base, exponent NumericExpression) FloatExpression {
 	return NewFloatFunc("POWER", base, exponent)
 }
@@ -202,12 +204,14 @@ func CHR(integerExpression IntegerExpression) StringExpression {
 	return newStringFunc("CHR", integerExpression)
 }
 
+// CONCAT adds two or more expressions together
 func CONCAT(expressions ...Expression) StringExpression {
 	return newStringFunc("CONCAT", expressions...)
 }
 
-func CONCAT_WS(expressions ...Expression) StringExpression {
-	return newStringFunc("CONCAT_WS", expressions...)
+// CONCAT_WS adds two or more expressions together with a separator.
+func CONCAT_WS(separator Expression, expressions ...Expression) StringExpression {
+	return newStringFunc("CONCAT_WS", append([]Expression{separator}, expressions...)...)
 }
 
 // CONVERT converts string to dest_encoding. The original encoding is
@@ -240,6 +244,7 @@ func DECODE(data StringExpression, format StringExpression) StringExpression {
 	return newStringFunc("DECODE", data, format)
 }
 
+// FORMAT formats a number to a format like "#,###,###.##", rounded to a specified number of decimal places, then it returns the result as a string.
 func FORMAT(formatStr StringExpression, formatArgs ...Expression) StringExpression {
 	args := []Expression{formatStr}
 	args = append(args, formatArgs...)
@@ -341,6 +346,7 @@ func TO_HEX(number IntegerExpression) StringExpression {
 	return newStringFunc("TO_HEX", number)
 }
 
+// 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, String(matchType[0], true))
diff --git a/internal/jet/select_table.go b/internal/jet/select_table.go
index e32d714..6894bc0 100644
--- a/internal/jet/select_table.go
+++ b/internal/jet/select_table.go
@@ -10,17 +10,14 @@ type SelectTableImpl struct {
 	selectStmt StatementWithProjections
 	alias      string
 
-	projections []Projection
+	projections ProjectionList
 }
 
 func NewSelectTable(selectStmt StatementWithProjections, alias string) SelectTableImpl {
 	selectTable := SelectTableImpl{selectStmt: selectStmt, alias: alias}
 
-	for _, projection := range selectStmt.projections() {
-		newProjection := projection.fromImpl(&selectTable)
-
-		selectTable.projections = append(selectTable.projections, newProjection)
-	}
+	projectionList := selectStmt.projections().fromImpl(&selectTable)
+	selectTable.projections = projectionList.(ProjectionList)
 
 	return selectTable
 }
diff --git a/internal/jet/statement.go b/internal/jet/statement.go
index 4523750..23909c2 100644
--- a/internal/jet/statement.go
+++ b/internal/jet/statement.go
@@ -39,7 +39,7 @@ type StatementWithProjections interface {
 }
 
 type HasProjections interface {
-	projections() []Projection
+	projections() ProjectionList
 }
 
 type SerializerStatementInterfaceImpl struct {
@@ -116,7 +116,7 @@ type StatementImpl struct {
 	Clauses []Clause
 }
 
-func (s *StatementImpl) projections() []Projection {
+func (s *StatementImpl) projections() ProjectionList {
 	for _, clause := range s.Clauses {
 		if selectClause, ok := clause.(ClauseWithProjections); ok {
 			return selectClause.projections()
diff --git a/mysql/functions.go b/mysql/functions.go
index 073d615..b4611f2 100644
--- a/mysql/functions.go
+++ b/mysql/functions.go
@@ -2,108 +2,182 @@ package mysql
 
 import "github.com/go-jet/jet/internal/jet"
 
+// ROW is construct one table row from list of expressions.
+var ROW = jet.ROW
+
 // ------------------ Mathematical functions ---------------//
 
-var POW = jet.POW
-var LN = jet.LN
-var LOG = jet.LOG
-
+// ABSf calculates absolute value from float expression
 var ABSf = jet.ABSf
+
+// ABSi calculates absolute value from int expression
 var ABSi = jet.ABSi
+
+// POW calculates power of base with exponent
+var POW = jet.POW
+
+// POWER calculates power of base with exponent
 var POWER = jet.POWER
+
+// SQRT calculates square root of numeric expression
 var SQRT = jet.SQRT
 
+// CBRT calculates cube root of numeric expression
 func CBRT(number jet.NumericExpression) jet.FloatExpression {
 	return POWER(number, Float(1.0).DIV(Float(3.0)))
 }
 
+// CEIL calculates ceil of float expression
 var CEIL = jet.CEIL
+
+// FLOOR calculates floor of float expression
 var FLOOR = jet.FLOOR
+
+// ROUND calculates round of a float expressions with optional precision
 var ROUND = jet.ROUND
+
+// SIGN returns sign of float expression
 var SIGN = jet.SIGN
+
+// TRUNC calculates trunc of float expression with precision
 var TRUNC = TRUNCATE
 
+// TRUNCATE calculates trunc of float expression with precision
 var TRUNCATE = func(floatExpression jet.FloatExpression, precision jet.IntegerExpression) jet.FloatExpression {
 	return jet.NewFloatFunc("TRUNCATE", floatExpression, precision)
 }
 
-var BIT_NOT = jet.BIT_NOT
+// LN calculates natural algorithm of float expression
+var LN = jet.LN
+
+// LOG calculates logarithm of float expression
+var LOG = jet.LOG
 
 // ----------------- Aggregate functions  -------------------//
 
+// AVG is aggregate function used to calculate avg value from numeric expression
+var AVG = jet.AVG
+
+// BIT_AND is aggregate function used to calculates the bitwise AND of all non-null input values, or null if none.
 var BIT_AND = jet.BIT_AND
+
+// BIT_OR is aggregate function used to calculates the bitwise OR of all non-null input values, or null if none.
 var BIT_OR = jet.BIT_OR
-var BOOL_AND = jet.BOOL_AND
-var BOOL_OR = jet.BOOL_OR
-var EVERY = jet.EVERY
+
+// COUNT is aggregate function. Returns number of input rows for which the value of expression is not null.
+var COUNT = jet.COUNT
+
+// MAXi is aggregate function. Returns maximum value of int expression across all input values
 var MAXi = jet.MAXi
+
+// MAXf is aggregate function. Returns maximum value of float expression across all input values
+var MAXf = jet.MAXf
+
+// MINi is aggregate function. Returns minimum value of int expression across all input values
 var MINi = jet.MINi
+
+// MINf is aggregate function. Returns minimum value of float expression across all input values
+var MINf = jet.MINf
+
+// SUMi is aggregate function. Returns sum of expression across all integer expression.
 var SUMi = jet.SUMi
 
+// SUMi is aggregate function. Returns sum of expression across all integer expression.
 var SUMf = jet.SUMf
-var AVG = jet.AVG
-var MAXf = jet.MAXf
-var MINf = jet.MINf
-var COUNT = jet.COUNT
 
 //--------------------- String functions ------------------//
 
-var REGEXP_LIKE = jet.REGEXP_LIKE
+// BIT_LENGTH returns number of bits in string expression
 var BIT_LENGTH = jet.BIT_LENGTH
+
+// CHAR_LENGTH returns number of characters in string expression
 var CHAR_LENGTH = jet.CHAR_LENGTH
+
+// OCTET_LENGTH returns number of bytes in string expression
 var OCTET_LENGTH = jet.OCTET_LENGTH
+
+// LOWER returns string expression in lower case
 var LOWER = jet.LOWER
+
+// UPPER returns string expression in upper case
 var UPPER = jet.UPPER
-var BTRIM = jet.BTRIM
+
+// LTRIM removes the longest string containing only characters
+// from characters (a space by default) from the start of string
 var LTRIM = jet.LTRIM
+
+// RTRIM removes the longest string containing only characters
+// from characters (a space by default) from the end of string
 var RTRIM = jet.RTRIM
-var CHR = jet.CHR
+
+// CONCAT adds two or more expressions together
 var CONCAT = jet.CONCAT
+
+// CONCAT_WS adds two or more expressions together with a separator.
 var CONCAT_WS = jet.CONCAT_WS
-var CONVERT = jet.CONVERT
-var CONVERT_FROM = jet.CONVERT_FROM
-var CONVERT_TO = jet.CONVERT_TO
-var ENCODE = jet.ENCODE
-var DECODE = jet.DECODE
+
+// FORMAT formats a number to a format like "#,###,###.##", rounded to a specified number of decimal places, then it returns the result as a string.
 var FORMAT = jet.FORMAT
-var INITCAP = jet.INITCAP
+
+// LEFT returns first n characters in the string.
+// When n is negative, return all but last |n| characters.
 var LEFT = jet.LEFT
+
+// RIGHT returns last n characters in the string.
+// When n is negative, return all but first |n| characters.
 var RIGHT = jet.RIGHT
 
+// LENGTH returns number of characters in string with a given encoding
 func LENGTH(str jet.StringExpression) jet.StringExpression {
 	return jet.LENGTH(str)
 }
 
+// LPAD fills up the string to length length by prepending the characters
+// fill (a space by default). If the string is already longer than length
+// then it is truncated (on the right).
 func LPAD(str jet.StringExpression, length jet.IntegerExpression, text jet.StringExpression) jet.StringExpression {
 	return jet.LPAD(str, length, text)
 }
+
+// RPAD fills up the string to length length by appending the characters
+// fill (a space by default). If the string is already longer than length then it is truncated.
 func RPAD(str jet.StringExpression, length jet.IntegerExpression, text jet.StringExpression) jet.StringExpression {
 	return jet.RPAD(str, length, text)
 }
 
+// MD5 calculates the MD5 hash of string, returning the result in hexadecimal
 var MD5 = jet.MD5
-var REPEAT = jet.REPEAT
-var REPLACE = jet.REPLACE
-var REVERSE = jet.REVERSE
-var STRPOS = jet.STRPOS
-var SUBSTR = jet.SUBSTR
-var TO_ASCII = jet.TO_ASCII
-var TO_HEX = jet.TO_HEX
 
-//----------Data Type Formatting Functions ----------------------//
-var TO_CHAR = jet.TO_CHAR
-var TO_DATE = jet.TO_DATE
-var TO_NUMBER = jet.TO_NUMBER
-var TO_TIMESTAMP = jet.TO_TIMESTAMP
+// REPEAT repeats string the specified number of times
+var REPEAT = jet.REPEAT
+
+// REPLACE replaces all occurrences in string of substring from with substring to
+var REPLACE = jet.REPLACE
+
+// REVERSE returns reversed string.
+var REVERSE = jet.REVERSE
+
+// SUBSTR extracts substring
+var SUBSTR = jet.SUBSTR
+
+// REGEXP_LIKE Returns 1 if the string expr matches the regular expression specified by the pattern pat, 0 otherwise.
+var REGEXP_LIKE = jet.REGEXP_LIKE
 
 //----------------- Date/Time Functions and Operators ------------//
-
+// CURRENT_DATE returns current date
 var CURRENT_DATE = jet.CURRENT_DATE
-var CURRENT_TIME = jet.CURRENT_TIME
-var CURRENT_TIMESTAMP = jet.CURRENT_TIMESTAMP
-var LOCALTIME = jet.LOCALTIME
-var LOCALTIMESTAMP = jet.LOCALTIMESTAMP
 
+// CURRENT_TIME returns current time with time zone
+func CURRENT_TIME(precision ...int) TimeExpression {
+	return TimeExp(jet.CURRENT_TIME(precision...))
+}
+
+// CURRENT_TIMESTAMP returns current timestamp with time zone
+func CURRENT_TIMESTAMP(precision ...int) TimestampExpression {
+	return TimestampExp(jet.CURRENT_TIMESTAMP(precision...))
+}
+
+// NOW returns current datetime
 func NOW(fsp ...int) DateTimeExpression {
 	if len(fsp) > 0 {
 		return jet.NewTimestampFunc("NOW", Int(int64(fsp[0]), true))
@@ -111,18 +185,24 @@ func NOW(fsp ...int) DateTimeExpression {
 	return jet.NewTimestampFunc("NOW")
 }
 
+// TIMESTAMP return a datetime value based on the arguments:
 func TIMESTAMP(str StringExpression) TimestampExpression {
 	return jet.NewTimestampFunc("TIMESTAMP", str)
 }
 
+// UNIX_TIMESTAMP returns unix timestamp
 func UNIX_TIMESTAMP(str StringExpression) TimestampExpression {
 	return jet.NewTimestampFunc("UNIX_TIMESTAMP", str)
 }
 
-// --------------- Conditional Expressions Functions -------------//
-var COALESCE = jet.COALESCE
-var NULLIF = jet.NULLIF
-var GREATEST = jet.GREATEST
-var LEAST = jet.LEAST
+//----------- Comparison operators ---------------//
+
+// EXISTS checks for existence of the rows in subQuery
 var EXISTS = jet.EXISTS
+
+// CASE create CASE operator with optional list of expressions
 var CASE = jet.CASE
+
+//----------------- Bit operators ---------------//
+
+var BIT_NOT = jet.BIT_NOT
diff --git a/postgres/functions.go b/postgres/functions.go
index fbded66..8f273aa 100644
--- a/postgres/functions.go
+++ b/postgres/functions.go
@@ -53,8 +53,8 @@ var CONCAT = func(expressions ...Expression) StringExpression {
 	return jet.CONCAT(explicitLiteralCasts(expressions...)...)
 }
 
-func CONCAT_WS(expressions ...Expression) StringExpression {
-	return jet.CONCAT_WS(explicitLiteralCasts(expressions...)...)
+func CONCAT_WS(separator Expression, expressions ...Expression) StringExpression {
+	return jet.CONCAT_WS(explicitLiteralCast(separator), explicitLiteralCasts(expressions...)...)
 }
 
 var CONVERT = jet.CONVERT