Question

I have these two tables (Article and Sale):

id  |  name     |
====+============
1   |   milk    |
2   |   apple   |
3   |   bread   |
... |    ...    |


id  |   idArticle  |   date     |
====+==============+=============
1   |       2      | 2011-01-01 |
2   |       2      | 2011-01-01 |
3   |       3      | 2011-01-01 |
4   |       1      | 2011-01-02 |
... |      ...     |    ...     |

I need to get the sales for 2011/01/01: article and count

2011-01-01 Milk 0
2011-01-01 Apple 2
2011-01-01 Bread 1
...

But I don’t know how to show “Milk: 0” because it didn’t sell milk that day.

This query doesn’t work:

SELECT s.date, a.name, COUNT(*)
FROM article a
LEFT JOIN sale s ON a.id = s.idArticle
WHERE s.date = "2011-01-01"
GROUP BY s.date, a.name

Answer 1

SELECT "2011-01-01" AS date, a.name, IFNULL(s.total, 0)
FROM article a
LEFT JOIN (
    SELECT idArticle, COUNT(*) AS total
    FROM sale
    WHERE date = "2011-01-01"
    GROUP BY idArticle
) AS s ON a.id = s.idArticle