mysql - 如何将相同的数据合并到水平表中

Question

我尝试并阅读了很多帖子，但我仍然不知道如何处理这个请求:

我有一个这样的表:

+------+------+------+|Device|PERIOD| DATE |+------+------+------+|A     |1     |1/1/11|+------+------+------+|A     |2     |2/1/11|+------+------+------+|B     |1     |3/1/11|+------+------+------+|B     |2     |4/1/11|+------+------+------+

我希望看到这样的输出:

+------+--------+--------+|Device|PERIOD 1|PERIOD 2|+------+--------+--------+|A     |1/1/11  |2/1/11  |+------+--------+--------+|B     |3/11/11 |4/1/11  |+------+--------+--------+

请帮帮我，谢谢:)

Answer 1

您可以在此处使用旋转逻辑:

SELECT
    Device,
    MAX(CASE WHEN PERIOD = 1 THEN DATE END) AS PERIOD1,
    MAX(CASE WHEN PERIOD = 2 THEN DATE END) AS PERIOD2
FROM yourTable
GROUP BY
    Device
ORDER BY
    Device;