2   具體內(nèi)容

 2.1  使用范圍

SQL Server（2008開(kāi)始） ；Azure SQL數(shù)據(jù)庫(kù)；Azure  SQL數(shù)據(jù)倉(cāng)庫(kù)；并行數(shù)據(jù)倉(cāng)庫(kù)

2.2  語(yǔ)法

 是SQL Server數(shù)據(jù)庫(kù)引擎評(píng)估以獲取單個(gè)數(shù)據(jù)值的符號(hào)和運(yùn)算符的組合。簡(jiǎn)單表達(dá)式可以是單個(gè)常量，變量，列或標(biāo)量函數(shù)。運(yùn)算符可用于將兩個(gè)或多個(gè)簡(jiǎn)單表達(dá)式連接到一個(gè)復(fù)雜的表達(dá)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 ]