Which of the following can be used instead of the equal (=) operator in a subquery to avoid the “Subquery returned more than 1 value” error in SQL Server?
A) NOT INB) BETWEENC) EXISTSD) IN
It should be C, becuase exist retern one value
The correct answer is C) EXISTS.
In SQL Server, subqueries can sometimes return multiple rows, which can lead to the “Subquery returned more than 1 value” error when using the equal (=) operator. To avoid this error, the EXISTS operator can be used instead.
The EXISTS operator checks for the existence of at least one record in the subquery, without returning the actual values. This allows for more precise filtering of results and avoids the issue of multiple values being returned.
For example, consider the following query:
SELECT * FROM orders WHERE order_id = (SELECT order_id FROM order_items WHERE product_id = '123')
If the subquery returns more than one order_id, the “Subquery returned more than 1 value” error will be thrown. However, by using the EXISTS operator, the query can be rewritten as:
SELECT * FROM orders WHERE EXISTS (SELECT 1 FROM order_items WHERE order_id = orders.order_id AND product_id = '123')
This query will return all orders that have at least one order item with a product_id of ‘123’, without encountering the subquery error.