Reference no: EM131934355

Question: Draw the query tree for each SQL. Explain what kinds of join methods are used in each query tree. Explain why one outperforms the other.

#1 .SELECT E.emp_no, E.first_name, E.last_name

FROM employees E

WHERE EXISTS ( SELECT S.emp_no

FROM salaries S WHERE S.emp_no = E.emp_no

INTERSECT SELECT DM.emp_no

FROM dept_manager DM

WHERE DM.emp_no = E.emp_no);

#2.SELECT DISTINCT E.emp_no, E.first_name, E.last_name

FROM employees E, salaries S, dept_manager DM

WHERE S.emp_no = E.emp_no AND DM.emp_no = E.emp_no