Question

我有一个包含以下条目的表格：

+------------+-----------+----------+
| screenId   | userInput | numInput |
+------------+-----------+----------+
| 13_1_2_1   | 2         |        9 |
| 13_1_2_2   | 2         |        9 |
| 13_1_2_2   | 3         |        2 |
| 13_1_2_2   | 9         |        2 |
| 13_1_2_2_2 | 3         |        3 |
| 13_1_2_2_2 | 5         |        2 |
| 13_2_2_2   | 4         |        4 |
| 13_2_2_2   | 5         |        4 |
| 13_2_2_2   | 7         |        2 |
+------------+-----------+----------+

我需要构建一个查询，将输出显示为：

+------------+---+---+---+---+---+---+---+---+---+---+
| screenId   | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
+------------+---+---+---+---+---+---+---+---+---+---+
| 13_1_2_1   | 0 | 0 | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 13_1_2_2   | 0 | 0 | 9 | 2 | 0 | 0 | 0 | 0 | 0 | 2 |
| 13_1_2_2_2 | 0 | 0 | 0 | 3 | 0 | 2 | 0 | 0 | 0 | 0 |
| 13_2_2_2   | 0 | 0 | 0 | 0 | 4 | 4 | 0 | 2 | 0 | 0 |
+------------+---+---+---+---+---+---+---+---+---+---+

这里0-9列值是userInput值，而它们的值是numInput值。例如，第一行表示值userInput'2'的numInput，screenID'13_1_2_1'表示'9'。

我无法为此问题构建正确的查询。请帮忙。

Answer 1

非常非常糟糕......

SELECT
    p.screenId,
    p0.numInput `0`,
    p1.numInput `1`,
    p2.numInput `2`,
    p3.numInput `3`,
    p4.numInput `4`,
    p5.numInput `5`,
    p6.numInput `6`,
    p7.numInput `7`,
    p8.numInput `8`,
    p9.numInput `9`,
FROM
    screens p
    LEFT JOIN screens p0 ON p0.screenId=p.screenId AND p0.userInput=0
    LEFT JOIN screens p1 ON p1.screenId=p.screenId AND p1.userInput=1
    LEFT JOIN screens p2 ON p2.screenId=p.screenId AND p2.userInput=2
    LEFT JOIN screens p2 ON p3.screenId=p.screenId AND p3.userInput=3
    LEFT JOIN screens p2 ON p4.screenId=p.screenId AND p4.userInput=4
    LEFT JOIN screens p2 ON p5.screenId=p.screenId AND p5.userInput=5
    LEFT JOIN screens p2 ON p6.screenId=p.screenId AND p6.userInput=6
    LEFT JOIN screens p2 ON p7.screenId=p.screenId AND p7.userInput=7
    LEFT JOIN screens p2 ON p8.screenId=p.screenId AND p8.userInput=8
    LEFT JOIN screens p2 ON p9.screenId=p.screenId AND p9.userInput=9
GROUP BY
    p.screenId

Answer 2

另一个非常糟糕的解决方案：）

SELECT DISTINCT screenId, 
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '0' ) as '0',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '1' ) as '1',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '2' ) as '2',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '3' ) as '3',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '4' ) as '4',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '5' ) as '5',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '6' ) as '6',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '7' ) as '7',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '8' ) as '8',
(select IF(sum(numInput) IS NOT NULL, sum(numInput), 0) from quest as q where q.screenId = quest.screenId and q.userInput = '9' ) as '9'
from quest;

我想有一个更好的解决方案，你的“枢轴”就像使用组操作符的结果表一样。我发现时会更新。

Answer 3

顺便提一下，标准解决方案（当表示层由于某些奇怪的原因而不可用时）如下。但请注意，表示OUTER JOIN实际上可能会快一些！

SELECT screenid
     , MAX(CASE WHEN userinput = 0 THEN numinput ELSE 0 END) '0'
     , MAX(CASE WHEN userinput = 1 THEN numinput ELSE 0 END) '1'
     , MAX(CASE WHEN userinput = 2 THEN numinput ELSE 0 END) '2'
     , MAX(CASE WHEN userinput = 3 THEN numinput ELSE 0 END) '3'
     , MAX(CASE WHEN userinput = 4 THEN numinput ELSE 0 END) '4'
     , MAX(CASE WHEN userinput = 5 THEN numinput ELSE 0 END) '5'
     , MAX(CASE WHEN userinput = 6 THEN numinput ELSE 0 END) '6'
     , MAX(CASE WHEN userinput = 7 THEN numinput ELSE 0 END) '7'
     , MAX(CASE WHEN userinput = 8 THEN numinput ELSE 0 END) '8'
     , MAX(CASE WHEN userinput = 9 THEN numinput ELSE 0 END) '9'
  FROM my_table
 GROUP
    BY screenid;

哦，并且调用列'0'，'1'，'2'，'3'等等正在打开一个痛苦的世界

如何在mysql中将列属性值显示为列

3 个答案: