[ WITH <common_table_expression> [ ,n ] ] <common_table_expression>::= expression_name [ ( column_name [ ,n ] ) ] AS ( CTE_query_definition ) 现在使用CTE来解决上面的问题,SQL语句如下: with cr as ( select CountryRegionCode from
YouTube – SQL WITH Clause | How to write SQL Queries using WITH Clause | SQL CTE (Common Table Expression) 特色 1. CTE 可以引用自身, 实现递归查询. (Oracle 用 connect by prior) 2. 它有点像表变量, 其后的 query 都可以引用它. 然后自动销毁. 很方便 3. 可读性很棒 复用与可读性优化 来看...
A Common Table Expression (CTE) in SQL is a one-time result set, i.e. it is a temporary table that exists only during the execution of a single query. It allows us to work with data specifically within that query, such as using it in SELECT, UPDATE, INSERT, DELETE, CREATE, VIEW,...
Common Table Expression Common table expression简称CTE,由SQL:1999标准引入,可以认为是在单个 SELECT、INSERT、UPDATE、DELETE 或 CREATE VIEW 语句的执行范围内定义的临时结果集。CTE 与派生表类似,具体表现在不存储为对象,并且只在查询期间有效。与派生表的不同之处在于,CTE 可自引用,还可在同一查询中引用多次。
The first common table expression is coloredgreen, the secondblue. As you can see from the SELECT statement the CTE’s are joined as if they were tables. Hopefully you can see that as your queries become more complicated, CTE’s can become a really useful way to separate operations; theref...
A valid identifier for the common table expression.expression_namemust be different from the name of any other common table expression defined in the sameWITH <common_table_expression>clause, butexpression_namecan be the same as the name of a base table or view. Any reference toexpression_name...
CommonTableExpression CommonTableExpression 建構函式 屬性 Columns ExpressionName QueryExpression 方法 CompositeGroupingSpecification CompressionDelayIndexOption CompressionDelayTimeUnit CompressionEndpointProtocolOption CompressionPartitionRange ComputeClause ComputeFunction ComputeFunctionType ConstraintDefinition Cons...
expression_name 公用表表达式的有效标识符。 expression_name 须不同于在同一WITH <common_table_expression>子句中定义的任何其他公用表表达式的名称,但可以与基表或基视图的名称相同。 在查询中对 expression_name 的任何引用都会使用公用表表达式,而不使用基对象。
SQL Server CTE (Common Table Expression) 公用表表达式,参考:Sql—CTE公用表表达式和With用法总结特色1.CTE可以引用自身,实现递归查询.(Oracle用 connectbyprior)2.它有点像表变量,其后的query都可以引用它.然后自动销毁.很方便3.可读性很棒...
有关详细信息,请参阅WITH common_table_expression。 NO_PERFORMANCE_SPOOL 适用于:SQL Server(从 SQL Server 2016(13.x)开始)和 Azure SQL 数据库。 防止将后台处理程序运算符添加到查询计划(在需要后台处理程序以确保有效的更新语义时的计划除外)。 在某些情况下,后台处理程序作员可以降低性能。 例如,如果有许多...