Add wiki Expressions page.
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wiki/Expressions.md
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wiki/Expressions.md
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Jet sql builder supports following expression types:
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- Bool expressions
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- Integer expressions
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- Float expressions
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- String expressions
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- Date expressions
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- Time expressions
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- Timez expressions (with time zone)
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- Timestamp expressions
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- Timestampz expressions (with time zone)
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_This list might be extended with feature Jet releases._
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### Literal type
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For every expression type there is a method to create one literal type expressions.
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Literal type examples:
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```
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Bool(true)
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Integer(11)
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Float(23.44)
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String("John Doe")
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Date(2010, 12, 3)
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Time(23, 6, 6, 1)
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Timez(23, 6, 6, 222, +200)
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Timestamp(2010, 10, 21, 15, 30, 12, 333)
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Timestampz(2010, 10, 21, 15, 30, 12, 444, 0)
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NULL
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STAR (alias for *)
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```
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### Column types
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Every sql builder table column belongs to one expression type. There are following column types:
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```
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ColumnBool
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ColumnInteger
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ColumnFloat
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ColumnString
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ColumnDate
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ColumnTime
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ColumnTimez
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ColumnTimestamp
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ColumnTimestampz
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```
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Columns and literals can form arbitrary expressions but have to follow valid SQL expression syntax.
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For instance valid expressions are:
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```
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Bool(true).AND(Bool(false)).IS_FALSE()
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(Film.Length.GT(Int(100)).AND(Film.Length.LT(Int(200))).IS_TRUE() // table 'film', integer column 'length'
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```
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Some of the invalid expressions. These expressions will cause go build to break.
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```
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Bool(true).AND(Int(11)) // can't compare bool and
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Int(11).ADD(Float(22.2)) // can't add integer and floats, but
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// using cast it is possible: Int(11).TO_FLOAT().ADD(Float(22.2))
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```
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## Common expression operators
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```go
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type Expression interface {
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clause
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projection
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groupByClause
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OrderByClause
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// Test expression whether it is a NULL value.
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IS_NULL() BoolExpression
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// Test expression whether it is a non-NULL value.
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IS_NOT_NULL() BoolExpression
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// Check if this expressions matches any in expressions list
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IN(expressions ...Expression) BoolExpression
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// Check if this expressions is different of all expressions in expressions list
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NOT_IN(expressions ...Expression) BoolExpression
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// The temporary alias name to assign to the expression
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AS(alias string) projection
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// Expression will be used to sort query result in ascending order
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ASC() OrderByClause
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// Expression will be used to sort query result in ascending order
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DESC() OrderByClause
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// Cast expression to dbType
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TO(dbType string) Expression
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// Cast expression to bool type
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TO_BOOL() BoolExpression
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// Cast expression to smallint type
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TO_SMALLINT() IntegerExpression
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// Cast expression to integer type
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TO_INTEGER() IntegerExpression
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// Cast expression to bigint type
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TO_BIGINT() IntegerExpression
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// Cast expression to numeric type, using precision and optionally scale
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TO_NUMERIC(precision int, scale ...int) FloatExpression
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// Cast expression to real type
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TO_REAL() FloatExpression
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// Cast expression to double precision type
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TO_DOUBLE() FloatExpression
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// Cast expression to text type
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TO_TEXT() StringExpression
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// Cast expression to date type
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TO_DATE() DateExpression
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// Cast expression to time type
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TO_TIME() TimeExpression
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// Cast expression to time with time timezone type
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TO_TIMEZ() TimezExpression
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// Cast expression to timestamp type
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TO_TIMESTAMP() TimestampExpression
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// Cast expression to timestamp with timezone type
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TO_TIMESTAMPZ() TimestampzExpression
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}
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```
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Examples:
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```go
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Film.Description.IS_NULL()
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Int(1).ADD(Int(2)).AS("1+2")
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(Film.Duration.ADD(Int(3))).ASC()
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String("1999-01-08 13:05:06 +0100 CET").TO_TIMESTAMPZ()
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```
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### Bool expression operators:
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```go
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type BoolExpression interface {
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Expression
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// Check if this expression is equal to rhs
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EQ(rhs BoolExpression) BoolExpression
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// Check if this expression is not equal to rhs
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NOT_EQ(rhs BoolExpression) BoolExpression
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// Check if this expression is distinct to rhs
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IS_DISTINCT_FROM(rhs BoolExpression) BoolExpression
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// Check if this expression is not distinct to rhs
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IS_NOT_DISTINCT_FROM(rhs BoolExpression) BoolExpression
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// Check if this expression is true
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IS_TRUE() BoolExpression
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// Check if this expression is not true
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IS_NOT_TRUE() BoolExpression
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// Check if this expression is false
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IS_FALSE() BoolExpression
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// Check if this expression is not false
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IS_NOT_FALSE() BoolExpression
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// Check if this expression is unknown
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IS_UNKNOWN() BoolExpression
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// Check if this expression is not unknown
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IS_NOT_UNKNOWN() BoolExpression
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// expression AND operator rhs
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AND(rhs BoolExpression) BoolExpression
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// expression OR operator rhs
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OR(rhs BoolExpression) BoolExpression
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}
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```
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Examples:
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```
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Staff.Active.EQ(Bool(true))
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Staff.Active.IS_TRUE()
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Bool(true).AND(Staff.Active).OR(Bool(false))
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```
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### Integer expression operators
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```go
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type IntegerExpression interface {
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Expression
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numericExpression
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// Check if expression is equal to rhs
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EQ(rhs IntegerExpression) BoolExpression
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// Check if expression is not equal to rhs
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NOT_EQ(rhs IntegerExpression) BoolExpression
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// Check if expression is distinct from rhs
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IS_DISTINCT_FROM(rhs IntegerExpression) BoolExpression
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// Check if expression is not distinct from rhs
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IS_NOT_DISTINCT_FROM(rhs IntegerExpression) BoolExpression
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// Check if expression is less then rhs
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LT(rhs IntegerExpression) BoolExpression
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// Check if expression is less then equal rhs
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LT_EQ(rhs IntegerExpression) BoolExpression
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// Check if expression is greater then rhs
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GT(rhs IntegerExpression) BoolExpression
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// Check if expression is greater then equal rhs
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GT_EQ(rhs IntegerExpression) BoolExpression
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// expression + rhs
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ADD(rhs IntegerExpression) IntegerExpression
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// expression - rhs
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SUB(rhs IntegerExpression) IntegerExpression
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// expression * rhs
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MUL(rhs IntegerExpression) IntegerExpression
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// expression / rhs
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DIV(rhs IntegerExpression) IntegerExpression
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// expression % rhs
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MOD(rhs IntegerExpression) IntegerExpression
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// expression ^ rhs
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POW(rhs IntegerExpression) IntegerExpression
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// expression & rhs
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BIT_AND(rhs IntegerExpression) IntegerExpression
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// expression | rhs
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BIT_OR(rhs IntegerExpression) IntegerExpression
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// expression # rhs
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BIT_XOR(rhs IntegerExpression) IntegerExpression
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// ~expression
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BIT_NOT() IntegerExpression
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// expression << rhs
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BIT_SHIFT_LEFT(shift IntegerExpression) IntegerExpression
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// expression >> rhs
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BIT_SHIFT_RIGHT(shift IntegerExpression) IntegerExpression
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}
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```
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Examples:
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```go
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(Film.Length.ADD(Int(20))).LT(Int(200))
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Film.LanguageID.EQ(Int(2))
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Film.LanguageID.BIT_SHIFT_LEFT(Int(2))
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```
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