How to display data without using JOIN and Counting Number of employees? - mysql

Question

I am having trouble with this question I can't seem to get the count correct
on each department and only select the highest one as well as excluding
"DALLAS"
THIS IS THE QUESTION
"Write a SQL statement to display the name and location of all departments
(except the departments located in Dallas) with the highest number of
employees.
You cannot use join operations in your SQL statement (e.g., … FROM department,
employee WHERE …, department INNER JOIN employee ON …)."
DEPARTMENT_ID DEPARTMENT_NAME LOCATION
------------- -------------------- --------------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 IT DALLAS
50 EXECUTIVE NEW YORK
60 MARKETING CHICAGO
6 rows selected
EMPLOYEE_ID EMPLOYEE_NAME JOB_TITLE SUPERVISOR_ID HIRE_DATE SALARY COMMISSION DEPARTMENT_ID
----------- -------------------- -------------------------------------------------- ------------- --------- ---------- ---------- -------------
7839 KING PRESIDENT 20-NOV-01 5000 50
7596 JOST VICE PRESIDENT 7839 04-MAY-01 4500 50
7603 CLARK VICE PRESIDENT 7839 12-JUN-01 4000 50
7566 JONES CHIEF ACCOUNTANT 7596 05-APR-01 3000 10
7886 STEEL PUBLIC ACCOUNTANT 7566 08-MAR-03 2500 10
7610 WILSON BUSINESS ANALYST 7596 03-DEC-01 3000 20
7999 WOLFE TEST ANALYST 7610 15-FEB-02 2500 20
7944 LEE REPORTING ANALYST 7610 04-SEP-06 2400 20
7900 FISHER SALES EXECUTIVE 7603 06-DEC-01 3000 500 30
7921 JACKSON SALES REPRESENTATIVE 7900 25-FEB-05 2500 400 30
7952 LANCASTER SALES CONSULTANT 7900 06-DEC-06 2000 150 30
7910 SMITH DATABASE ADMINISTRATOR 7596 20-DEC-01 2900 40
7788 SCOTT PROGRAMMER 7910 15-JAN-03 2500 40
7876 ADAMS PROGRAMMER 7910 15-JAN-03 2000 40
7934 MILLER PROGRAMMER 7876 25-JAN-02 1000 40
8000 BREWSTER TBA 22-AUG-13 2500
8100 PHILLIPS TBA 7839 21-AUG-13 2800
7400 SMITH VICE PRESIDENT 7839 16-FEB-01 4300 50
7700 ANDRUS PUBLIC ACCOUNTANT 7566 18-FEB-02 2500 10
7601 SAMPSON PROGRAMMER 7910 09-JAN-01 2500 40
7588 DODSON TEST ANALYST 7610 02-AUG-08 2500 20
7888 SANDY SALES CONSULTANT 7900 05-AUG-04 2500 30
22 rows selected
SELECT DEPARTMENT_NAME,
location,
count(*)
FROM DEPARTMENT
WHERE department_id IN ( SELECT department_id
FROM department
WHERE UPPER(location) <> 'DALLAS'
)
group by department_NAME, location
ORDER BY location;
DEPARTMENT_NAME LOCATION COUNT(*)
-------------------- -------------------- ----------
MARKETING CHICAGO 1
SALES CHICAGO 1
ACCOUNTING NEW YORK 1
EXECUTIVE NEW YORK 1

Answer 1

you can try using sub-queries if you are limited in not using joins
SELECT *
FROM (SELECT d.department_name,
d.location,
(SELECT COUNT(employee_id)
FROM employee e
WHERE e.department_id = d.department_id) no_employees
FROM department d
WHERE d.location <> 'DALLAS'
) t
WHERE no_employees = (SELECT COUNT(employee_id)
FROM employee
WHERE department_id IN (SELECT DISTINCT department_id
FROM department
WHERE location <> 'DALLAS')
GROUP BY department_id
ORDER BY 1 DESC
LIMIT 1)
Result
department_name location no_employees
SALES CHICAGO 4
EXECUTIVE NEW YORK 4

Answer 2

Am trying to the find the department with maximum count and then retrieve the corresponding name and location without using joins
SELECT (SELECT DEPARTMENT_NAME, location
FROM DEPARTMENT
WHERE department_id = q.department_id) ,
q.ct countofdept
FROM
(SELECT count(*) ct, department_id
FROM EMPLOYEE
WHERE department_id in ( SELECT department_id
FROM department
WHERE UPPER(location) <> 'DALLAS'
)
GROUP BY department_id
ORDER BY ct desc
LIMIT 1) q