Question

I have two SQL SELECT COUNT statements:

SELECT COUNT(*) FROM table1 t1 
INNER JOIN table2 t2 ON t2.id = t1.rowid
WHERE t1.flag1 = false AND t2.flag2 = true;

SELECT COUNT(*) FROM table1 t1 
INNER JOIN table2 t2 ON t2.id = t1.rowid
WHERE t1.flag1 = true AND t2.flag2 = false;

As can be seen the only difference of these two statements are the flipped condition.

But what I want to do is to combine the two statements into one so that the output becomes one table with two columns, the first column contains the result of the first statement and the second column contains the result of the second statement. Something like:

   count1   |   count 2
-------------------------
    3456    |     9864

---

I use PostgreSQL by the way. Can someone let me know how to do this?

Many thanks

Answer 1

This should do it for you. I’m not to familiar with PostgreSql but I think it will work.

SELECT 
    SUM(CASE WHEN t1.Flag1 = false AND t2.flag2 = true THEN 1 ELSE 0 END) Count1,
    SUM(CASE WHEN t1.Flag1 = true AND t2.flag2 = false THEN 1 ELSE 0 END) Count2
FROM 
    table1 t1 
    INNER JOIN table2 t2 ON t2.id = t1.rowid