Choosing the join column
- SQL course
- Intermediate
- Lesson 2/115
- 4 min
Learn the difference between USING and ON.
Matching column choice
When joining equally named columns, USING is a shortcut. For different names use ON.
SELECT * FROM orders
INNER JOIN customers
USING (customer_id);USING works when customer_id is in both tables.
All columns are selected from orders. customers USING is joined, keeping only matching rows.
Matching column choice — details
USING is only for same-named columns. When names differ, ON must be written explicitly.
For example, if both orders and customers have customer_id, you write USING (customer_id); the column then appears only once in the result.
Practice Matching column choice
Join using the customer_id column with USING.
Starter code
-- join with using
SELECT *
FROM orders
INNER JOIN customersSample solution
SELECT *
FROM orders
INNER JOIN customers
USING (customer_id);Expected output
order_id customer_id 1 10 2 11
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Add USING
SELECT * FROM orders
INNER JOIN customers
____ (customer_id);SELECT * FROM orders
INNER JOIN customers
USING (customer_id);Explanation: When both tables share the column name you can write USING (customer_id) instead of ON.
2 When is USING used?
- When the column names are the same Correct answer
- When the column names are different
- Always
- Never
Explanation: USING is only for same-named columns.
3 Choosing the join column: match the terms
| Term | Meaning |
|---|---|
USING |
same name |
ON |
different name |
WHERE |
filter |
AS |
alias |