Php, MySql Sum from two tables - php

Question

I'm trying to make this query work:
SELECT
IFNULL(SUM(days), 0) AS days
FROM
`table_days`
WHERE task = 1
GROUP BY task
UNION
ALL
SELECT
IFNULL(SUM(total), 0) AS total
FROM
`table_total`
WHERE task = 1
GROUP BY task ;
I have two tables :
1. table_days
id task days
==========================
1 1 3.00
2 1 2.00
2. table_total
id task total
==========================
1 3 0.00
The query above partially works, the result is:
stdClass Object
(
[days] => 5.00
)
but I would like to get the result from second table even if there are no records found. Something like
stdClass Object
(
[days] => 5.00
[total] => 0.00
)

Answer 1

Try This query
SELECT
IFNULL(SUM(days), 0) AS days
FROM
`table_days`
WHERE task = 1
GROUP BY task
UNION
ALL
SELECT
SUM(case when task = 1 then IFNULL(total,0) else 0 end) AS total
FROM
`table_total`
GROUP BY task ;

Answer 2

This code will work for you (example at sqlfiddle):
SELECT
IFNULL(SUM(days), 0) AS value, 'days' as name
FROM
`table_days`
WHERE task = 1
GROUP BY task
UNION ALL
(SELECT CASE WHEN u.value = -1 then 0 else value end as value, 'total' as name
FROM
(
SELECT
IFNULL(SUM(total), 0) AS value
FROM
`table_total`
WHERE task = 1
GROUP BY task
UNION
SELECT -1 as value
) u
);
And it will return:
+-------+-------+
| value | name |
+-------+-------+
| 5 | days |
| 0 | total |
+-------+-------+

Answer 3

The conundrum with your current approach is that the second half of your UNION query doesn't "know" anything about the tasks which appear in the first half.
However, joining the two tables would allow you to leverage the relationship between the two tables. I think a better way of doing this would be to LEFT JOIN the table_days table with table_total, thereby retaining all tasks:
SELECT t1.task, t1.sum_days, t2.sum_total
FROM
(
SELECT task, IFNULL(SUM(days), 0) AS sum_days
FROM `table_days`
GROUP BY task
) t1
LEFT JOIN
(
SELECT task, IFNULL(SUM(total), 0) AS sum_total
FROM `table_total`
GROUP BY task
) t2
ON t1.task = t2.task
WHERE t1.task = 1
If you want to include all tasks from the table_days table, you can remove the WHERE clause.