Joins in sql

SQL subqueries are basic tools if you want to communicate effectively with relational databases. In this article, I provide five subquery examples demonstrating how to use scalar, multirow, and correlated subqueries in the WHERE, FROM/JOIN, and SELECT clauses.

A subquery, or nested query, is a query placed within another SQL query.

When requesting information from a database, you may find it necessary to include a subquery into the , , , or clause. However, you can also use subqueries when updating the database (i.e.

What is a subquery

in , , and statements).

There are several types of SQL subqueries:

• Scalar subqueries return a single value, or exactly one row and exactly one column.
• Multirow subqueries return either:
  • One column with multiple rows (i.e.

    a list of values), or

  • Multiple columns with multiple rows (i.e. tables).
• Correlated subqueries, where the inner query relies on information obtained from the outer query.

You can read more about the different types of SQL subqueries elsewhere; here, I want to focus on examples.

As we all know, it’s always easier to grasp

how to put subquery in sql

how to use subquery in join sql