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.
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...
CTEs or common table expressions, which are new in SQL Server 2005, provide an easy way to break a complex SQL statement down into smaller more manageable queries. CTEs are is some ways very much like views. Unlike a view which can be created once and used by many SQL statements, a CTE...
A CTE can be used to: Create a recursive query. For more information, seeRecursive Queries Using Common Table Expressions. Substitute for a view when the general use of a view is not required; that is, you do not have to store the definition in metadata. Enable grouping by a column that...
https://dev.mysql.com/blog-archive/mysql-8-0-1-recursive-common-table-expressions-in-mysql-ctes-part-four-depth-first-or-breadth-first-traversal-transitive-closure-cycle-avoidance/
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...
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...
MySQL 8.0 Labs: [Recursive] Common Table Expressions in MySQL (CTEs), Part Three - hierarchies Posted on Oct 25, 2016 by Guilhem Bichot Category: Optimizer Tags: optimizer [Update of April 2017: the features discussed here are now also available in the official release 8.0....
When working with SQL Server™ 2005, I prefer a third option of using Common Table Expressions (CTEs). CTEs can help improve the readability (and thus the maintainability) of the code without compromising performance. They also make writing recursive code in T-SQL significantly easier than it...
This topic provides reference information about Common Table Expressions (CTEs) in both SQL Server and PostgreSQL. It explains that CTEs are part of the ANSI SQL standard and are used to simplify queries and improve readability by defining temporary views or derived ta...