Question

如果我有一个如下所示的MySQL表：

id  |   cat_id  |   name    |   date
------------------------------------
1   |   1       |   suzy    |   2011-09-15
2   |   2       |   andy    |   2011-10-01
3   |   1       |   dony    |   2010-12-25
4   |   3       |   harry   |   2010-01-05
5   |   2       |   matty   |   2011-06-01
6   |   3       |   samy    |   2010-11-02
7   |   1       |   honey   |   2011-10-03

如何选择是否需要结果：

cat_id  | id |
-------------
1   | 7  |
2   | 2  |
3   | 6  |

Answer 1

SELECT cat_id, id
  FROM mytable t
 WHERE NOT EXISTS (
        SELECT *
          FROM mytable
         WHERE cat_id = t.cat_id
           AND date > t.date
       )

Answer 2

SELECT cat_id, id
FROM (SELECT cat_id, name
      FROM table
      ORDER BY date DESC) AS h
GROUP BY cat_id
ORDER BY cat_id ASC

替换table

Answer 3

尝试此查询 -

SELECT c1.cat_id, c1.id FROM catalog c1
  JOIN (SELECT cat_id, MAX(date) last_date FROM catalog GROUP BY cat_id) c2
    ON c1.cat_id = c2.cat_id AND c1.date = c2.last_date;

从表格中的每个类别中选择最新的一个

3 个答案: