Subqueries: Using Queries Within Other Queries

A subquery is a select statement that is nested inside another select, insert, update, or delete statement, inside a conditional statement, or inside another subquery.

You can also express subqueries as join operations. See Chapter 4, "Joins: Retrieving Data from Several Tables."

How subqueries work

Subquery syntax

Subquery restrictions

Example of using a subquery

Qualifying column names

Subqueries with correlation names

Multiple levels of nesting

Subqueries in update, delete, and insert statements

Subqueries in conditional statements

Using subqueries instead of expressions

Types of subqueries

Expression subqueries

Quantified predicate subqueries

Subqueries used with in

Subqueries used with not in

Subqueries using not in with NULL

Subqueries used with exists

Subqueries used with not exists

Finding intersection and difference with exists

Using correlated subqueries

Correlated subqueries containing Transact-SQL outer joins

Correlated subqueries with correlation names

Correlated subqueries with comparison operators

Correlated subqueries in a having clause


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