Question

I will simplfy this:

I have two SQL expressions which works OK:

First:

select count(*) as number1
 from T1
where DATE1>'2012-01-01' and DATE2<'2012-12-31'

Result:13

select  count(*) as number2 
from T1
where DATE3>DATE2 and CURDATE()>DATE2

Result:5

But when I try to insert those two COUNTS in GROUP BY I am getting as resulyt always 13!!!

SELECT NAME,
 COUNT(case when DATE1>'2012-01-01' and DATE2<'2012-12-31' then 1 else 0 end) as number1, 
COUNT (case when (DATE3>DATE2 and CURDATE()>DATE2) then 1 else 0 end) as number 2
from T1

I am getting as result:

NAME  NUMBER1  NUMBER2
A       5         5
B       4         4
C       4         4

But I should get:

NAME  NUMBER1  NUMBER2
A       5         4
B       4         0
C       4         1

So that SUM of columns be 13 and 5 like in first two queries . What am I doing wrong?
Thank you

Answer 1

COUNT(expression) counts not null expressions. You can modify your query by changing the ELSE 0 to ELSE NULL or by removing it (the ELSE NULL is implied at CASE expressions):

SELECT name,
    COUNT(CASE WHEN date1 > '2012-01-01' AND date2 < '2012-12-31' 
              THEN 1 END
         ) AS number1, 
    COUNT(CASE WHEN date3 > date2 AND CURDATE() > date2 
              THEN 1 END
         ) AS number2
FROM T1 
GROUP BY name ;