Question

In SQL how do you show 0 if record is null?

select sales_id, totalbuy, totalsell, totalbuy + totalsell as total from
(select sales_id, SUM(CASE WHEN side= 'buy' THEN 1 ELSE 0 END) AS totalbuy, 
SUM(CASE WHEN side= 'sell' THEN 1 ELSE 0 END) AS totalsell 
from car_orders 
where sales_id in ('sales1', 'sales2', 'sales3', 'sales4')only
GROUP BY sales_id)q
order by total desc
limit 0, 10;

After car_orders I have tried inserting*(car_orders+ISNULL(car_orders,0)) but get an error.

Answer 1

Building from Sohnee’s answer, here is the SQL I think you want to use:

SELECT 
    sales_id,
    IFNULL(totalbuy, 0),
    IFNULL(totalsell, 0),
    IFNULL(totalbuy, 0) + IFNULL(totalsell, 0) as total
FROM
(
    SELECT
        sid as sales_id,
        SUM(CASE WHEN side = 'buy' THEN 1 ELSE 0 END) AS totalbuy, 
        SUM(CASE WHEN side = 'sell' THEN 1 ELSE 0 END) AS totalsell 
    FROM 
        ( SELECT 'sales1' as sid UNION SELECT 'sales2' UNION SELECT 'sales3' UNION SELECT 'sales4' ) mysalesids
    LEFT OUTER JOIN car_orders
      ON sales_id = sid
    GROUP BY
       sales_id
) q
ORDER BY total DESC
LIMIT 0, 10;

The key to the above is the “LEFT OUTER JOIN”. If you can have the ‘sales1’, ‘sales2’, ‘sales3’ values in their own table, that would be preferable rather than having a sub-select.

Hope this helps,

john…