Nested Queries and Subqueries

What is a Subquery?

Subquery in WHERE

-- students scoring above the average
SELECT name, marks FROM students
WHERE marks > (SELECT AVG(marks) FROM students);

Subquery with IN

-- students who have paid fees
SELECT name FROM students
WHERE roll_no IN (SELECT roll_no FROM fees);

Summary

• A subquery is a query inside another; the inner runs first.
• Common with WHERE, IN and comparison operators.

Subquery क्या है?

WHERE में Subquery

-- average से ज़्यादा अंक वाले students
SELECT name, marks FROM students
WHERE marks > (SELECT AVG(marks) FROM students);

IN के साथ Subquery

-- जिन students ने fees दी
SELECT name FROM students
WHERE roll_no IN (SELECT roll_no FROM fees);

सारांश

• Subquery एक query के अंदर दूसरी है; inner पहले चलती है।
• WHERE, IN और comparison operators के साथ common।