Question

take the above as an output of a sample table,
I need an sql query which results “2” as the count from the table.

i’ve tried intially while sentby column upto 4, and was okay;
but more rows shows incorrect o/p. my older code is given

SELECT COUNT(*)/2
     FROM 
     (SELECT sentby,sentto
     FROM
          (SELECT DISTINCT sentby, sentto FROM count_temp)
     WHERE sentto IN
          (SELECT DISTINCT sentby FROM count_temp )
      AND sentby IN
          (SELECT DISTINCT sentto FROM count_temp )
     ) ;

Thanks in advance:) and appreciated.

Answer 1

Your query:

with cte as (
select distinct m1.sentby , m1.sentto
from m m1 
inner join m m2
   on m1.sentby = m2.sentto and
      m2.sentby = m1.sentto 
)
select count(*)/2 from cte;

test it at sqlfiddle

Also, simplifying:

select count( distinct m1.sentby ) / 2
from m m1 
inner join m m2
   on m1.sentby = m2.sentto and
      m2.sentby = m1.sentto