Fetch Rows Including Unmatched With LEFT JOIN

Return all rows from the left table and matching rows from the right, filling NULL where no match exists.

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

Docker-validated Not currently validation-green

Example 1

Show all customers including those with no orders

Carol has no matching row in orders, so her total is NULL. Alice and Bob match normally. ORDER BY c.id keeps the result deterministic.

Source table data Rows loaded before the example query runs.

Setup

CREATE TABLE customers (id INT, name VARCHAR(50));

CREATE TABLE orders (id INT, customer_id INT, total INT);

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

INSERT INTO
  orders (id, customer_id, total)
VALUES
  (1, 1, 99),
  (2, 2, 149);

Validated query Shared across supported engines.

SQL

SELECT
  c.name,
  o.total
FROM
  customers c
  LEFT JOIN orders o ON c.id = o.customer_id
ORDER BY
  c.id;

Expected result Returned rows for the shared example.

name	total
Alice	99
Bob	149
Carol	NULL

Output is identical across all engines.

Useful when

Where this command helps.

showing all primary records even when related data is missing
finding unmatched rows on the right side of a relationship

Explanation

What the command is doing.

LEFT JOIN keeps every row from the left table regardless of whether a matching row exists in the right table. Columns from the right table are NULL for unmatched rows. This is useful for finding missing relationships, such as customers who have never placed an order.

Fetch Rows Including Unmatched With LEFT JOIN

Show all customers including those with no orders

Where this command helps.

What the command is doing.

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