If a column reference is made from an inner query to an outer query, then it must be fully qualified with the appropriate table name from the FROM clause of the outer query.
Any subquery must contain a FROM clause, and every column referenced in the SELECT statement must be in a table referenced either in the FROM clause for the subquery or some FROM clause in an outer query containing the subquery.
| SQL Statement Main Query | FROM Clause Required |
|---|---|
|
No. |
|
Optional. |
| DELETE | Optional, depending on the syntax used. |