Subquery Fundamental
A subquery is a ‘Select’ query placed inside another query or SQL statement. A subquery can be used with a SELECT, INSERT, UPDATE, or DELETE statement and is generally placed within a WHERE, HAVING, or FROM clause of the outer or main query.
The subqueries can generally take one of the below formats:
WHERE expression [NOT] IN (subquery)
WHERE expression comparison_operator [ANY | ALL] (subquery)
WHERE [NOT] EXISTS (subquery)
The general syntax of subquery is:
SELECT column_name(s)
FROM table_name
WHERE column_name operator
(SELECT column_name
FROM table_name
WHERE condition);
SQL Server Subquery
In SQL Server, Subqueries are a powerful feature used to perform complex queries and combine data from multiple tables or multiple data sets. Subqueries can be used in different business cases and in different scenarios to join data from an inner query with an outer query. In this article let us see what is a subquery, where it can be used, and how to build a subquery.