当其他列为空时，如何在mysql列中显示结果？

Question

I have the following query:

SELECT 
    (IFNULL(daily_clicks, 0)), 
    (IFNULL(daily_score, 0)), 
    (SELECT SUM(`daily_score`) FROM `user_score` `n`) AS total 
FROM
`user_score` `t` WHERE `userid`="123123" AND t.created='2015-06-27' LIMIT 1;

If i change the date to where data exist i see the total user_score, but when i select where there are no results for that specific date, i get nothing back (even in the sum).

How do i get the sum column to appear even if other does not? Thx

Answer 1

If the date doesn't exist, then the query returns no rows.

One method is to use aggregation:

SELECT coalesce(sum(daily_clicks), 0), 
       coalesce(sum(daily_score), 0)
FROM `user_score` `t`
WHERE `userid` = 123123 AND t.created = '2015-06-27';

This will guarantee that one row returns, even when there are no matches. If you want each daily_click , you can use group_concat() :

SELECT group_concat(daily_clicks),
       coalesce(sum(daily_score), 0)
FROM `user_score` `t`
WHERE `userid` = 123123 AND t.created = '2015-06-27';

This still returns one row, but with multiple daily_clicks values concatenated in one column.