Have you ever wondered what’s possible with the ON keyword in SQL joins? I know I have. Specifically, I’ve seen people use logical AND conditions after the ON keyword, and it got me thinking: can we join two tables on multiple conditions?
The short answer is yes, we can. But there’s more to it than that.
## Joining on Multiple Conditions
When joining two tables, we typically use the ON keyword to specify the common column(s) between them. But what if we need to join on multiple conditions? That’s where the AND operator comes in.
For example, let’s say we have two tables, `orders` and `customers`, and we want to join them on both `customer_id` and `order_date`. We can do this:
SELECT *
FROM orders
JOIN customers
ON orders.customer_id = customers.customer_id AND orders.order_date = customers.order_date;As long as the joining columns have the same data type, we can add as many conditions as we need using the AND operator.
## Using OR Operator in JOINS
Now, what about the OR operator? Can we use it in joins as well? The answer is yes, but with a twist.
We can use the OR operator in joins, but we need to be careful with the parentheses to avoid any confusion. Here’s an example:
SELECT *
FROM orders
JOIN customers
ON orders.customer_id = customers.customer_id OR orders.order_date = customers.order_date;In this case, the join will be performed if either the `customer_id` or `order_date` conditions are met.
## Conclusion
The ON keyword in SQL joins is more powerful than you might think. By using the AND and OR operators, we can create more complex joins that meet our specific needs. Just remember to keep your conditions clear and your parentheses in check.
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*Further reading: [SQL Join Tutorial](https://www.w3schools.com/sql/sql_join.asp)*