How to Use EXISTS in MySQL

1 year ago
Emily Johnson
1 minute

In MySQL, the EXISTS keyword is used to check whether a subquery returns any rows. Its syntax is as follows:

SELECT column1, column2, ...
FROM table_name
WHERE EXISTS (subquery);

For example, suppose we have two tables: orders and customers, and we want to check if any customers have placed an order. We can use the EXISTS keyword to perform this query.

SELECT *
FROM customers
WHERE EXISTS (
    SELECT *
    FROM orders
    WHERE orders.customer_id = customers.id
);

This will return customers who have placed orders. If the subquery returns any rows, EXISTS will return true; otherwise, it will return false.

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