Nested SELECT Statements in SQLite Examples

There are different ways to form a nested SELECT statement in SQLite. This section covers practical examples of nested SELECT statements in SQLite.

Nested SELECT Statement in SQLite Using IN Operator Example

In this example, we are going to a form a nested SELECT statement with the help of IN operator.

This query displays all the details from table w3wiki where a student has taken courses of duration 6 months.

Query:

SELECT *
FROM w3wiki 
WHERE id In (SELECT courses.id FROM courses 
    WHERE courses.id = w3wiki.id AND courses.duration = 6);

Output:

Explanation: There is only one course in courses table of duration ‘6’ months i.e. ‘Python’ taken by id’s 1001 and 1004. That is the same id’s displayed in the output block.

Nested SELECT Statement in SQLite Using Exists Operator

In this example, we are going to use exists operator. When using Exists operator, parent query will only run if the child query returns a True value.

This query will display all the records of ‘w3wiki’ table only if there are courses in ‘courses’ table where duration is greater than 4 months.

Query:

SELECT *
FROM w3wiki 
WHERE EXISTS ( SELECT 1 FROM courses 
   WHERE courses.id = w3wiki.id AND courses.duration > 4 );

Output:

Explanation: In the above image, we can clearly notice all the records from ‘w3wiki’ table get displayed. Since all the records of courses table has course duration greater than 4 months.

Conclusion

A nested SELECT statement consists of two parts i.e. a parent query and child query. A parent query result generally depends on the result of child query or subquery. Using nested SELECT queries allows users to perform more complex data retrieval operations in SQLite.

This article covered all the basic concepts related to the topic with clear and concise examples along with there explanations.

A nested SELECT statement is a statement in which a SELECT statement is used within another SELECT statement. Nested SELECT queries or subqueries are used in SQLite to perform complex operations.

This article explains how to use nested SELECT statements in SQLite by covering all the basic structures and concepts of nested SELECT Statements in SQLite. It will also cover the practical applications of nested SELECT queries with examples.