Multiple conditions in SQL - sql

Question

I have following table:
Employee ID Employee Status Date of Termination
1 A NULL
2 A NULL
3 I 1/1/2016
4 I 12/15/2016
5 I 1/1/2016
I would like to report on the following:
Number of current active employees - 2
Number of inactive employees - 3
Number of employees terminated in last one month - 2
This is the piece of code I used:
select
case when employee_status='A' then count(employee_id) else '' end,
case when employee_status='I' then count(employee_id) else '' end,
case when employee_status='I'
then
(select count(employee_id)
from employee
where date_of_termination between '1/1/2016' and '2/1/2016')
else '' end
from employee
My result set is:
Active | Inactive | Inactive_last_month
2 | 0 | 0
0 | 3 | 2
I would like to achieve the following:
Active | Inactive | Inactive_last_month
2 | 3 | 2
Any recommendations will be appreciated.

Answer 1

You need to SUM up the number of rows that match each criteria:
SELECT
SUM(CASE WHEN date_of_termination IS NULL THEN 1 ELSE 0 END) AS active,
SUM(CASE WHEN date_of_termination IS NOT NULL THEN 1 ELSE 0 END) AS inactive,
SUM(CASE WHEN date_of_termination BETWEEN '20160101' AND '20160201' THEN 1 ELSE 0 END) AS inactive_last_month
FROM
Employee
I've ignored the employee_status column with the assumption that the date is sufficient to determine whether or not the employee is active/inactive - in which case that column probably shouldn't even exist in the table since it's duplicating data.

Answer 2

This should be possible to simplify it using SUM :
select
sum(case when employee_status='A' then 1 else 0 end) as active,
sum(case when employee_status='I' then 1 else 0 end) as inactive,
sum(case when employee_status='I' and date_of_termination between '1/1/2016' and '2/1/2016' then 1 else 0 end) as inactive_last_month
from employee

Answer 3

I woudl wrap the case satements in sum() function and also modify the ELSE part of the CASE Statement to be 0.
so it will look like something like this:
select
SUM(case when employee_status='A' then count(employee_id) else 0 end) AS Active,
SUM(case when employee_status='I' then count(employee_id) else 0 end) AS Inactive,
SUM(case when employee_status='I'
then
(select count(employee_id)
from employee
where date_of_termination between '1/1/2016' and '2/1/2016')
else 0 end) AS Inactive_last_month
from employee