What is an EXISTS Operator?
The EXISTS operator makes the subquery returns only the records that are present in the result set of the of query. It will return TRUE if the sub-query has one or more rows, if not it will return FALSE. EXISTS operator is regularly employed in conjunction with correlated sub-queries, where the first query is related to outer columns.
Syntax:
SELECT column1 FROM table1 WHERE EXISTS (SELECT * FROM table2 WHERE table2.column = table1.column);
Explanation: In the above Syntax, the EXISTS operator checks whether there are any rows in table2 that match the condition specified in the subquery. If at least one row exists, the outer query returns true.
Subqueries and EXISTS in MariaDB
Subqueries and EXISTS are powerful tools in MariaDB that enable us to write complex and efficient queries. Subqueries allow us to nest one query inside another and provide a flexible way to retrieve data. The EXISTS operator, on the other hand, it checks for the existence of rows returned by a subquery. In this article, we will look at what subqueries are, how they work, and how the EXISTS operator can be used to extend their functionality in MariaDB.