Getting Count based on values of multiple rows of the same column

Question

I am relatively new to database. Say that if I have table like below:

PHeader AHeader IHeader

p1       a1      0

p1       a1      2

p1       a1      3

p1       a2      0

p1       a3      0

p1       a4      0

p1       a4      2

p1       a4      3

p2       a5      0

The expected output is :

PHeader BCount  TCount


p1          2    2

p2          0    1

BCount: is for the given PHeader and AHeader Value, if the IHeader values has all the values of (0,2 &3) then BCount value of PHeader is increased by 1 , Since for the p1 it has a1 & a4 with all the vaues of 0,2 & 3 as IHeader Values the BCount for p1 is given as 2

TCount: is for given given PHeader and AHeader value , if IHeader value has only 0 but not 2 or 3, then TCount for the given PHeader is increased by 1. Hence the TCount for p1 is given as 2.

Could you please give me tips in writing the query?

Answer 1

You can approach this using two aggregations. The inner one aggregates at the pheader , aheader level. This counts the values that you are interested in.

The outer one applies the logic that you've described to these summaries:

select pheader,
       sum(ih_0 > 0 and ih_2 > 0 and ih_3 > 0) as bcount,
       sum(ih_0 > 0 and (ih_2 = 0 or ih_3 = 0)) as tcount
from (select pheader, aheader,
             sum(iheader = 0) as ih_0,
             sum(iheader = 2) as ih_2,
             sum(iheader = 3) as ih_3
      from table t
      group by pheader, aheader 
     ) pa
group by pheader;

EDIT:

The question is tagged MySQL. The following will work in both databases:

select pheader,
       sum(case when ih_0 > 0 and ih_2 > 0 and ih_3 > 0 then 1 else 0 end) as bcount,
       sum(case when ih_0 > 0 and (ih_2 = 0 or ih_3 = 0) then 1 else 0 end) as tcount
from (select pheader, aheader,
             sum(case when iheader = 0 then 1 else 0 end) as ih_0,
             sum(case when iheader = 2 then 1 else 0 end) as ih_2,
             sum(case when iheader = 3 then 1 else 0 end) as ih_3
      from table t
      group by pheader, aheader 
     ) pa
group by pheader;

Answer 2

Please check beloq sql query

SELECT 
PHeader ,
COUNT(*) as BCount  , --total 
SUM(CASE WHEN PHeader = 'p1' THEN 1 ELSE 0 END) as TCount  

FROM yourtablename group by PHeader

Hope this will give you some idea.