To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Subqueries can contain GROUP BY and ORDER BY clauses - This option is true. Subqueries can contain GROUP BY and ORDER BY clauses to perform aggregations or sort the data within the subquery.
Option B) Main query and subquery can get data from different tables - This option is true. The main query and subquery can retrieve data from different tables. In fact, one of the main uses of subqueries is to retrieve data from related tables.
Option C) Main query and subquery must get data from the same tables - This option is false. The main query and subquery can get data from different tables. They can even have different conditions or criteria to retrieve data.
Option D) Subqueries can contain ORDER BY but not the GROUP BY clause - This option is false. Subqueries can contain both the ORDER BY and GROUP BY clauses. These clauses can be used to sort or group the data within the subquery.
Option E) Only one column or expression can be compared between the main query and subquery - This option is false. Multiple columns or expressions can be compared between the main query and subquery. This allows for more complex conditions and comparisons.
Option F) Multiple columns or expressions can be compared between the main query and subquery - This option is true. Multiple columns or expressions can be compared between the main query and subquery. This allows for more flexibility in filtering and retrieving the desired data.
Based on the explanations above, the correct statements regarding subqueries are:
A. Subqueries can contain GROUP BY and ORDER BY clauses.
B. The main query and subquery can get data from different tables.
F. Multiple columns or expressions can be compared between the main query and subquery.
Therefore, the correct answer is A, B, and F.