Check For NULL Values With IS NULL

Use `IS NULL` and `IS NOT NULL` to filter rows based on whether a column has a value.

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

Docker-validated Not currently validation-green

Example 1

Find employees who have no manager

Alice has no manager (NULL), so she is the top-level employee. WHERE manager_id = NULL would return no rows because comparisons with NULL are never true — IS NULL is the correct operator. Use IS NOT NULL to find the opposite: all employees who do have a manager.

Source table data Rows loaded before the example query runs.

Setup

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

INSERT INTO
  employees (id, name, manager_id)
VALUES
  (1, 'Alice', NULL),
  (2, 'Bob', 1),
  (3, 'Carol', 1);

Validated query Shared across supported engines.

SQL

SELECT
  name
FROM
  employees
WHERE
  manager_id IS NULL
ORDER BY
  name;

Expected result Returned rows for the shared example.

name
Alice

Output is identical across all engines.

Useful when

Where this command helps.

finding rows with missing or unset values
identifying top-level records with no parent reference

Explanation

What the command is doing.

NULL represents a missing or unknown value. It cannot be compared with = or != — those comparisons always evaluate to unknown. The correct operators are IS NULL to find missing values and IS NOT NULL to find rows that have a value. This distinction matters in WHERE clauses, JOIN conditions, and CASE expressions.

Check For NULL Values With IS NULL

Find employees who have no manager

Where this command helps.

What the command is doing.

Keep moving through nearby tasks.