Jan 2, 2025 · In this article, We will learn about Subquery in a SELECT statement by understanding various examples and output in detail. A subquery (also known as a nested query or inner query) is a query placed inside another query. The subquery returns a result that is used by the outer query.

We can use a SQL subquery to embed SELECT statements in a SELECT statement. Subqueries can also be embedded within the FROM and WHERE clause.

Based on the shape of the data each clause accepts, you can embed the appropriate subquery: The subquery in the SELECT clause can return a single value. The subquery in the FROM or INNER JOIN clauses can return a result set. The subquery in the WHERE clause can return a single value. We’ll use the employees table from the HR sample database:

Nov 22, 2024 · In Transact-SQL, a subquery can be substituted anywhere an expression can be used in SELECT, UPDATE, INSERT, and DELETE statements, except in an ORDER BY list. The following example illustrates how you might use this enhancement.

Oct 4, 2022 · This article showed you what you need to know about SQL subqueries and how to use them with the SELECT statement. However, subqueries are not limited to the SELECT statement only. You can use subqueries in all the CRUD operations of SQL – INSERT, SELECT, UPDATE, and DELETE.

Oct 12, 2024 · In this tutorial, we’ll explore using subqueries in SELECT, WHERE, and FROM clauses and show how to handle them when they become repetitive (and redundant). All our examples are based on our University database schema.

Jan 10, 2025 · In SQL, a subquery can be defined as a query embedded within another query. It is often used in the WHERE, HAVING, or FROM clauses of a statement. Subqueries are commonly used with SELECT, UPDATE, INSERT, and DELETE statements to achieve complex filtering and data manipulation.

Feb 13, 2025 · A subquery is usually added within the WHERE Clause of another SQL SELECT statement. You can use the comparison operators, such as >, <, or =. The comparison operator can also be a multiple-row operator, such as IN, ANY, or ALL.

Dec 13, 2013 · When you use a subquery in a select clause, Oracle essentially treats it as a left join (you can see this in the explain plan for your query), with the cardinality of the rows being just one on the right for every row in the left. Explanation for the left join.

Mar 25, 2025 · In this query: The subquery is executed first. It searches the departments table and returns the department_id of the ‘Sales’ department.; Next, the outer query is executed. It retrieves the department_id returned by the subquery and returns all employees whose department_id matches with the retrieved one.; This is how queries, including subqueries, are …