Which three statements are true regarding single row subqueries?
A.They must be placed on the left side of the comparison operator or condition B.They must return a row to prevent errors in the SQL statement C.They can be used in the HAVING clause. D.A SQL statement may have multiple single row subquery blocks E.They can be used in the WHERE clause F.They must be placed on the right side of the comparison operator or condition正确答案CDE
