Не специалист в области mysql, прошу помочь с составлением запроса. У меня два запроса. Первый удаляет все записи старше установленного времени. Второй очищается таблицы полностью.

DELETE FROM dt17e_quiz_r_student_quiz WHERE c_date_time < '2017-01-01 00:00:00' 
DELETE FROM dt17e_quiz_r_student_question WHERE c_stu_quiz_id NOT IN (SELECT c_id FROM dt17e_quiz_r_student_quiz); 
DELETE FROM dt17e_quiz_r_student_choice WHERE c_sq_id NOT IN (SELECT c_id FROM dt17e_quiz_r_student_question); 


DELETE FROM dt17e_quiz_r_student_quiz WHERE c_quiz_id =234;
DELETE FROM dt17e_quiz_r_student_question WHERE c_stu_quiz_id NOT IN (SELECT c_id FROM dt17e_quiz_r_student_quiz);
DELETE FROM dt17e_quiz_r_student_choice WHERE c_sq_id NOT IN (SELECT c_id FROM dt17e_quiz_r_student_question);

Допустим ли синтаксис (объединение удалить до определенной даты):

DELETE FROM dt17e_quiz_r_student_quiz WHERE c_date_time < '2017-01-01 00:00:00' c_quiz_id =234;