What is subquery in SQL with examples?

A Subquery or Inner query or a Nested query is a query within another SQL query and embedded within the WHERE clause. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. A subquery cannot be immediately enclosed in a set function.

What do you mean by subquery?

A subquery is a query that is nested inside a SELECT , INSERT , UPDATE , or DELETE statement, or inside another subquery. In this example a subquery is used as a column expression named MaxUnitPrice in a SELECT statement.

What are the types of subquery?

Types of SQL Subqueries

• Single Row Subquery. Returns zero or one row in results.
• Multiple Row Subquery. Returns one or more rows in results.
• Multiple Column Subqueries. Returns one or more columns.
• Correlated Subqueries.
• Nested Subqueries.

What is subquery in MySQL?

A subquery in MySQL is a query, which is nested into another SQL query and embedded with SELECT, INSERT, UPDATE or DELETE statement along with the various operators. A subquery is known as the inner query, and the query that contains subquery is known as the outer query.

Which is faster joins or subqueries?

The advantage of a join includes that it executes faster. The retrieval time of the query using joins almost always will be faster than that of a subquery. By using joins, you can maximize the calculation burden on the database i.e., instead of multiple queries using one join query.

What is difference between query and subquery?

A Subquery is a type of query which is written inside another query. A subquery becomes a part of a larger query. A subquery is also called INNER QUERY OR NESTED QUERY. A subquery is basically a SELECT statement that is embedded in a clause of another SQL statement.

What is the difference between subquery and join?

Joins and subqueries are both used to combine data from different tables into a single result. Subqueries can be used to return either a scalar (single) value or a row set; whereas, joins are used to return rows. A common use for a subquery may be to calculate a summary value for use in a query.

What is a subquery and its types?

A subquery, or nested query, is a query placed within another SQL query. SQL subqueries may return single values or entire tables. There can be nested subqueries or correlated subqueries. Each of these subquery types works well for certain use cases.

What are the three types of results a subquery can return?

Subquery Rules A subquery can fall into one of three types; scalar, row and table. A scalar subquery returns a single value, a row subquery returns several columns from a single record and a table subquery returns several rows.

Under what circumstances would you not be able to use a subquery?

You cannot include text, unitext, or image datatypes in subqueries. Subqueries cannot manipulate their results internally, that is, a subquery cannot include the order by clause, the compute clause, or the into keyword.

What is subquery, and what are its basic characteristics?

A subquery is a query within another query, also known as a nested query. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. Subqueries are used with the SELECT, INSERT, UPDATE, and DELETE statements.

Where clause in subquery SQL?

A subquery is a SQL query nested inside a larger query. The subquery can be nested inside a SELECT, INSERT, UPDATE, or DELETE statement or inside another subquery. A subquery is usually added within the WHERE Clause of another SQL SELECT statement. You can use the comparison operators, such as >, <, or =.

What is a scalar sub-query?

Scalar Subqueries Definition of a Scalar Subquery A scalar subquery is a subquery expression that can return a maximum of one value. As is true of other types of subqueries, there are two types of scalar subqueries: Correlated A correlated scalar subquery returns a single value for each row of its correlated outer tabl…

What is sub in SQL?

SQL Sub queries are the queries which are embedded inside another query. The embedded queries are called as INNER query & container query is called as OUTER query. The subqueries are the queries which are executed inside of another query. The result SQL query totally depends on the result of a subquery.