EXISTS Condition

EXISTS Condition

The EXISTS condition is considered "to be met" if the subquery returns at least one row.

The syntax for the EXISTS condition is:

SELECT columns
FROM tables
WHERE EXISTS ( subquery );




Example #1:

Let's take a look at a simple example. The following is an SQL statement that uses the EXISTS condition:

SELECT *
FROM suppliers
WHERE EXISTS
(select *
from orders
where suppliers.supplier_id = orders.supplier_id);

This select statement will return all records from the suppliers table where there is at least one record in the orders table with the same supplier_id.



Example #2 - NOT EXISTS:

The EXISTS condition can also be combined with the NOT operator.

For example,

SELECT *
FROM suppliers
WHERE not exists (select * from orders Where suppliers.supplier_id = orders.supplier_id);

This will return all records from the suppliers table where there are no records in the orders table for the given supplier_id.

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