Question

When one SQL query is embedded in another SQL query, the top-level SQL query can still contain an SQL ________ clause.

a) UNIQUE IN

b) WHERE IN

c) FROM or SORT BY

d) GROUP BY

Answer 1

The top-level SQL query when embedding another SQL query can contain an 'SQL WHERE IN' class. This structure involving subqueries allows the main query to refine results based on the output of the inner query.

Step-by-step explanation:

When one SQL query is embedded in another SQL query, the top-level SQL query can still contain an SQL WHERE IN clause. This type of query, where one query is nested inside another, is known as a subquery or inner query, and it is a powerful tool in SQL for filtering, aggregating, and organizing data. The inner query executes first, and its results are passed to the outer query, which can then utilize a WHERE clause to further refine those results. For example:

SELECT *
FROM Orders
WHERE OrderID IN (
SELECT OrderID
FROM Customers
WHERE CustomerName = 'CompanyXYZ'
);

In this example, the inner query selects order IDs for a specific customer, and the outer query then retrieves the complete records for those orders. The WHERE IN clause is essential in connecting the subquery results with the main query.