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Introduction to the Oracle subquery. A subquery is a SELECT statement nested inside another statement such as SELECT, INSERT, UPDATE, or DELETE. Typically, you can use a subquery anywhere that you use an expression. Consider this following subquery example that uses the products table from the sample database.
This tutorial introduces you to the SQL subquery and shows you how to use the subqueries to form flexible SQL statements.
13 Δεκ 2013 · When you use a subquery in a select clause, Oracle essentially treats it as a left join (you can see this in the explain plan for your query), with the cardinality of the rows being just one on the right for every row in the left.
This Oracle tutorial explains how to use Oracle subqueries with syntax and examples. A subquery is a query within a query. In Oracle, you can create subqueries within your SQL statements.
Use subqueries for the following purposes: To define the set of rows to be inserted into the target table of an INSERT or CREATE TABLE statement. To define the set of rows to be included in a view or materialized view in a CREATE VIEW or CREATE MATERIALIZED VIEW statement.
The WITH clause, or subquery factoring clause, is part of the SQL-99 standard and was added into the Oracle SQL syntax in Oracle 9.2. The WITH clause may be processed as an inline view or resolved as a temporary table.
Introduction. This tutorial shows you how to write subqueries. It uses the bricks and colours table. Run the queries below to see their contents: select * from bricks; select * from colours; Note: This tutorial makes heavy use of group by. If you want a refresher on this, check out module 7 of Databases for Developers: Foundations. Module 2.
