What are Nested Select Statements?
A nested select statement is a kind of select statement that is contained in other SQL statements like SELECT, INSERT, UPDATE or DELETE. The inner SELECT is executed first and then its result is used by the outer expression to do more operations.
Syntax:
SELECT column1, column2, ... FROM table1 WHERE column1 = (SELECT column1 FROM table2 WHERE condition);
Explanation:
- column1, column2, … – are the columns you want to retrieve from the outer query.
- table1: It is the table you’re querying in the outer query.
- table2: It is the table you’re querying in the inner query.
- WHERE condition – It is the condition used to filter data in the inner query.
What is Nested Select Statement in MariaDB
Nested select statements, normally named subqueries, represent an advanced feature for MariaDB which enables more efficient and thorough querying of the data. Therefore, the nesting of a SELECT statement within another allows us to perform operations and filtering that could be hardly possible with only one query.
In this article, we’ll explore the syntax and multiple examples of nested select statements in MariaDB.