Select (SQL): Difference between revisions

Revision as of 09:03, 5 January 2021

Revision as of 22:12, 4 March 2021

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Since 1999 the SQL standard allows named subqueries called [[common table expression]]s (named and designed after the IBM DB2 version 2 implementation; Oracle calls these [[subquery factoring]]). CTEs can also be [[recursive]] by referring to themselves; [[Hierarchical and recursive queries in SQL|the resulting mechanism]] allows tree or graph traversals (when represented as relations), and more generally [[fixpoint]] computations.

=== InlineDerived viewtable ===

AnA Inlinederived viewtable is the use of referencing an SQL subquery in a FROM clause. Essentially, the inlinederived viewtable is a subquery that can be selected from or joined to. Derived Inline Viewtable functionality allows the user to reference the subquery as a table. The inlinederived viewtable also is referred to as aan ''derivedinline tableview'' or a ''subselect''. Inline view functionality was introducedselect in Oraclefrom 9ilist''.

In the following example, the SQL statement involves a join from the initial Books table to the Inlinederived viewtable "Sales". This inlinederived viewtable captures associated book sales information using the ISBN to join to the Books table. As a result, the inlinederived viewtable provides the result set with additional columns (the number of items sold and the company that sold the books):

<syntaxhighlight lang="sql">