What is subquery in SQL?
- A subquery is a SQL query within a query. Nested queries that provide data to the enclosing query.
- Can be used in SELECT, INSERT, UPDATE, and DELETE statements
- Subqueries can be used to retrieve data from multiple tables and can be used as an alternative to a join
- Subqueries can also be used inside the WHERE or HAVING clause of the SELECT, INSERT, UPDATE, and DELETE statements
SELECT Column names FROM Table1 WHERE ColumnName [Comparison Operator] (SELECT ColumnName FROM Table2 WHERE [Condition]);
[Comparison Operator] could be equality operators such as =, >, <, >=, <=. I or LIKE operator