Nest A Query Inside Another With Subqueries

Embed a `SELECT` inside another query to filter, compute, or supply values that depend on aggregated or derived data.

5/5 supported engines validation-green 1 example 2 scenarios

Docker-validated Not currently validation-green

Example 1

Find employees who earn above the company average

The inner query computes the average salary (72500). The outer query then filters to only the rows where salary exceeds that value. Alice (70000) and Bob (50000) fall below the average and are excluded.

Source table data Rows loaded before the example query runs.

Setup

CREATE TABLE employees (id INT, name VARCHAR(50), salary INT);

INSERT INTO
  employees (id, name, salary)
VALUES
  (1, 'Alice', 70000),
  (2, 'Bob', 50000),
  (3, 'Carol', 90000),
  (4, 'Dave', 80000);

Validated query Shared across supported engines.

SQL

SELECT
  name,
  salary
FROM
  employees
WHERE
  salary > (
    SELECT
      AVG(salary)
    FROM
      employees
  )
ORDER BY
  salary DESC;

Expected result Returned rows for the shared example.

name	salary
Carol	90000
Dave	80000

Output is identical across all engines.

Useful when

Where this command helps.

comparing rows against a derived value like an average or maximum
breaking a query into nested logical steps without a separate table

Explanation

What the command is doing.

A subquery is a SELECT wrapped in parentheses and used where a value or table is expected. In a WHERE clause it computes a scalar value to compare against. In a FROM clause it acts as a derived table. Subqueries are evaluated once per logical step and can reference outer query columns to become correlated subqueries.

Nest A Query Inside Another With Subqueries

Find employees who earn above the company average

Where this command helps.

What the command is doing.

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