Question

A self-join can only be specified in the FROM clause with the use of the JOIN... keywords?

1) ON
2) USING
3) WHERE
4) AND

Answer 1

In SQL, a self-join is specified in the FROM clause using the JOIN keyword along with ON, USING, or WHERE, but not with AND alone, as AND is for chaining conditions.

Step-by-step explanation:

The question is asking about the syntax used in SQL when performing a self-join. A self-join is a join where a table is joined with itself. This is useful in scenarios where you have related data in the same table, and you need to relate rows of that table to each other based on some criteria. The correct syntax to specify a self-join involves using the JOIN keyword in conjunction with one of the options provided: ON, USING, or a conditional expression in the WHERE clause. Although AND can be used within the ON or WHERE clause to chain conditions, it is not by itself used to specify a self-join. Therefore, options 1) ON, 2) USING, and 3) WHERE are valid syntaxes to specify a self-join, with option 4) AND being part of the condition rather than the method of joining.