The first two statements are true about co-related subqueries:

1. The tables used in the main query are also used in a co-related sub-query: This is true. A correlated subquery is a subquery that uses values from the outer query. In other words, it has a reference to a table that also appears in the outer query.

2. The sub-queries which reference a column used in the main query are called co-related sub-queries: This is also true. The defining characteristic of a correlated subquery is that it uses a column from the outer query in its WHERE clause.

The last two statements are false:

3. The sub-queries which are written without parenthesis are called co-related sub-queries: This is false. All SQL subqueries must be enclosed in parentheses.

4. The sub-queries which mandatorily use different tables than those used in the main query are called co-related sub-queries: This is also false. As mentioned above, a correlated subquery is defined by its use of a column from the outer query, not by the tables it uses.

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The first two statements are true about co-related subqueries:

1. The tables used in the main query are also used in a co-related sub-query: This is true. A correlated subquery is a subquery that uses values from the outer query. In other words, it has a reference to a table that also appears in the outer query.

2. The sub-queries which reference a column used in the main query are called co-related sub-queries: This is also true. The defining characteristic of a correlated subquery is that it uses a column from the outer query in its WHERE clause.

The last two statements are false:

3. The sub-queries which are written without parenthesis are called co-related sub-queries: This is false. All SQL subqueries must be enclosed in parentheses.

4. The sub-queries which mandatorily use different tables than those used in the main query are called co-related sub-queries: This is also false. As mentioned above, a correlated subquery is defined by its use of a column from the outer query, not by the tables it uses.

Knowee AI · Accepted Answer

The first two statements are true about co-related subqueries:

1. The tables used in the main query are also used in a co-related sub-query: This is true. A correlated subquery is a subquery that uses values from the outer query. In other words, it has a reference to a table that also appears in the outer query.

2. The sub-queries which reference a column used in the main query are called co-related sub-queries: This is also true. The defining characteristic of a correlated subquery is that it uses a column from the outer query in its WHERE clause.

The last two statements are false:

3. The sub-queries which are written without parenthesis are called co-related sub-queries: This is false. All SQL subqueries must be enclosed in parentheses.

4. The sub-queries which mandatorily use different tables than those used in the main query are called co-related sub-queries: This is also false. As mentioned above, a correlated subquery is defined by its use of a column from the outer query, not by the tables it uses.

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