SQL Writing Subqueries 2

Question 1

Which keyword tests whether a subquery returns any rows at all?

Accepted Answer

EXISTS

Answer

EXISTS returns TRUE if the subquery produces one or more rows.

Question 2

A subquery that references a column from the outer query is called what?

Accepted Answer

Correlated subquery

Answer

A correlated subquery depends on a column supplied by the outer query and runs per outer row.

Question 3

What does a scalar subquery return?

Accepted Answer

A single value

Answer

A scalar subquery returns exactly one row and one column, i.e., a single value.

Question 4

Which operator lets a value match ANY result from a subquery returning multiple rows?

Accepted Answer

IN

Answer

IN checks whether a value matches any value in the subquery's result set.

Question 5

Where can a subquery used as a derived table appear?

Accepted Answer

In the FROM clause

Answer

A derived table is a subquery placed in the FROM clause and must be given an alias.

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