2   具體內容

 2.1  使用范圍

SQL Server（2008開始） ；Azure SQL數據庫；Azure  SQL數據倉庫；并行數據倉庫

2.2  語法

 是SQL Server數據庫引擎評估以獲取單個數據值的符號和運算符的組合。簡單表達式可以是單個常量，變量，列或標量函數。運算符可用于將兩個或多個簡單表達式連接到一個復雜的表達式中。

— Syntax for SQL Server and Azure SQL Database
{ constant | scalar_function | [ table_name. ] column | variable
| ( expression ) | ( scalar_subquery )
| { unary_operator } expression
| expression { binary_operator } expression
| ranking_windowed_function | aggregate_windowed_function
}
— Syntax for Azure SQL Data Warehouse and Parallel Data Warehouse
— Expression in a SELECT statement
<expression> ::=
{
constant
| scalar_function
| column
| variable
| ( expression )
| { unary_operator } expression
| expression { binary_operator } expression
}
[ COLLATE Windows_collation_name ]
— Scalar Expression in a DECLARE, SET, IF…ELSE, or WHILE statement
<scalar_expression> ::=
{
constant
| scalar_function
| variable
| ( expression )
| (scalar_subquery )
| { unary_operator } expression
| expression { binary_operator } expression
}
[ COLLATE { Windows_collation_name ]