CTE也就是common table expressions是sql标准里的语法,很多数据库都能够支持,MySQL也在8.0版本里加入了CTE功能,主要包括非递归的CTE以及递归CTE,这次我们讨论非递归CTE,相关内容参考Non-recursive Common Table Expression。 示例语法: WITHquery_nameAS(subquery)SELECT*FROMquery_name; CTE与derived table的一个不同点...
这个WITH 中可以没有 RETURNING 子句,因为外面没有引用 t 的主SQL 。这样写SQL没有什么意义,它会删除 foo 表和 bar 表中的所有数据,但是返回给客户端的影响行数只有 "DELETE FROM bar" 的结果,没有 "DELETE FROM foo" 的结果。 小结:在 WITH 中修改数据,是一个完全独立于主SQL的部分,也就是说,无论主S...
在测试递归查询的结果时,可以通过在 INSERT、UPDATE、DELETE 或 SELECT 语句的 OPTION 子句中使用 MAXRECURSION 提示和 0 到 32,767 之间的值,来限制特定语句允许的递归级数。有关详细信息,请参阅查询提示 (Transact-SQL)和WITH common_table_expression (Transact-SQL)。 伪代码和语义 递归CTE 结构必须至少包含一...
UNION, EXCEPT, or INTERSECT. For more information about how to use recursive CTE query definitions, see the following "Remarks" section andRecursive Queries Using Common Table Expressions.
A Common Table Expressions (CTE) is a temporary result set in SQL that we can reference within aSELECT,INSERT,UPDATE, orDELETEstatement. CTEs make complex queries more readable and maintainable. Example WITHRecentCustomersAS(SELECT*FROMCustomersWHEREage <30)SELECT*FROMRecentCustomers; ...
3. 总结 在MySQL 8.0 中引入CTE新特性，在大多数场景下，能够简化SQL，提高可读性，同时也能使用CTE代替视图，提高整体性能。另外CTE也能实现递归查询，下一篇文章将详细介绍。本文译自：https://www.percona.com/blog/2020/02/10/introduction-to-mysql-8-0-common-table-expressions-part-1/ ...
For more information, see the Remarks section and CREATE VIEW (Transact-SQL).If more than one CTE_query_definition is defined, the query definitions must be joined by one of these set operators: UNION ALL, UNION, EXCEPT, or INTERSECT.Guidelines for creating and using common table expressions...
Guidelines for defining and using recursive common table expressions Show 4 more Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric ...
在MySQL 8.0 中引入CTE新特性,在大多数场景下,能够简化SQL,提高可读性,同时也能使用CTE代替视图,提高整体性能。另外CTE也能实现递归查询,下一篇文章将详细介绍。 本文译自: https://www.percona.com/blog/2020/02/10/introduction-to-mysql-8-0-common-table-expressions-part-1/...
We’ve already seen there are several good reasons to use SQL CTE’s. Let’s look at each of these, in turn, using examples. By the time we’re done, you’ll see how to use one or more Common Table Expressions in a statement to work with joins. Also, you’ll see how you can...