What are the different types of SQL joins?
Updated 2026-07-10 · Beginner friendly
Quick answer
A join combines rows from two tables based on a related column. An inner join returns only rows that match in both tables. A left join returns all rows from the left table plus matches from the right. A right join does the opposite. A full outer join returns all rows from both tables, matched where possible.
The four common joins
- Inner join: only rows with a match in both tables.
- Left join: all left rows, with matching right rows or nulls.
- Right join: all right rows, with matching left rows or nulls.
- Full outer join: all rows from both, matched where possible.
SELECT c.name, o.id
FROM customers c
LEFT JOIN orders o ON o.customer_id = c.id;
-- returns every customer, even those with no ordersIn the interview
Interviewers often ask when you would use a left join. A great example is listing all customers including those with no orders, which an inner join would drop. Tying the join type to a real need is what they want to hear.
Common follow up questions
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