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B.2. Expressions
An expression represents a single value in context, although in some cases that value may change as the query is evaluated. For example, a literal value, such as 5 represents an integer value. A column reference such as "table.EmployeeName" represents a column in a data source and may take on many values while the command is being evaluated.
Expression- base expression interfaceColumnReference- represents an column in the data sourceLiteral- represents a literal scalar value, but may also be multi-valued in the case of bulk updates.Function- represents a scalar function with parameters that are also ExpressionsAggregateFunction- represents an aggregate function which holds a single expressionWindowFunction- represents a window function which holds an AggregateFunction (which is also used to represent analytical functions) and a WindowSpecificationScalarSubquery- represents a subquery that returns a single valueSearchedCase, SearchedWhenClause- represents a searched CASE expression. The searched CASE expression evaluates the criteria in WHEN clauses until one of them evaluates to TRUE, then evaluates the associated THEN clause.Array- represents an array of expressions, currently only used by the engine in multi-attribute dependent joins - see the supportsArrayType capability.
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