Correlated Subqueries

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Correlated Subqueries

A correlated subquery references columns from the outer query. It is evaluated once for each row processed by the outer query to perform row-specific logic.

snippet.sql
sql
SELECT e1.name
FROM employees e1
WHERE e1.salary > (
  SELECT AVG(e2.salary)
  FROM employees e2
  WHERE e2.department_id = e1.department_id
);

Breakdown

WHERE e1.salary > (

Initiates a comparison between a row value and the result of the subquery.

WHERE e2.department_id = e1.department_id

The correlation step that links the subquery to the current outer row's department.

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Correlated Subqueries

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