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A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.
Common table expressions and recursive queries [ edit ] SQL:1999 added a WITH [RECURSIVE] construct allowing recursive queries, like transitive closure , to be specified in the query language itself; see common table expressions .
MySQL Workbench now uses ANTLR4 as backend parser and has a new auto-completion engine that works with object editors (triggers, views, stored procedures, and functions) in the visual SQL editor and in models. The new versions add support for new language features in MySQL 8.0, such as common-table expressions and roles.
A derived table is the use of referencing an SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected from or joined to. The derived table functionality allows the user to reference the subquery as a table. The derived table is sometimes referred to as an inline view or a subselect.
The derived table also is referred to as an inline view or a select in from list. In the following example, the SQL statement involves a join from the initial Books table to the derived table "Sales". This derived table captures associated book sales information using the ISBN to join to the Books table.
The nested set model is a technique for representing nested set collections (also known as trees or hierarchies) in relational databases.. It is based on Nested Intervals, that "are immune to hierarchy reorganization problem, and allow answering ancestor path hierarchical queries algorithmically — without accessing the stored hierarchy relation".
This page was last edited on 7 November 2012, at 09:24 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.
For example, the composition of Employee and Dept is their join as shown above, projected on all but the common attribute DeptName. In category theory , the join is precisely the fiber product . The natural join is arguably one of the most important operators since it is the relational counterpart of logical AND.