Question

我们说我有一张这样的桌子

id  col1  col2  col3  col4  col5  col6
1    1     2     3     4     5     6
2    2     1     4     3     6     5
3    1     1     2     3     4     5

我想要选择每个字段具有不同值的行。输出将是

id  col1  col2  col3  col4  col5  col6
1    1     2     3     4     5     6
2    2     1     4     3     6     5

我知道你可以做到这一点

SELECT * FROM table
WHERE col1 <> col2 AND col2 <> col3...

但是这将需要永远这么多列。是否有特定的功能来确定所有列是否都是唯一的？

Answer 1

您可以使用UNION ALL

对您的表格进行取消操作

SELECT id
FROM (
  SELECT id, col1 AS col
  FROM mytable

  UNION ALL

  SELECT id, col2
  FROM mytable

  UNION ALL

  SELECT id, col3
  FROM mytable

  UNION ALL

  SELECT id, col4
  FROM mytable

  UNION ALL

  SELECT id, col5
  FROM mytable

  UNION ALL

  SELECT id, col6
  FROM mytable) AS t
GROUP BY id
HAVING COUNT(DISTINCT col) = 6

如果您希望选择所有列，则执行以下操作：

SELECT *
FROM mytable 
WHERE id IN ( .... above query here ...)

不幸的是，MySQL没有UNPIVOT运算符会使上述查询更简洁。

Answer 2

比您的解决方案稍微冗长一点，但如果列数过大则无法完美扩展：

SELECT
    *    -- In actual live code you would of course never use '*'
FROM
    MyTable
WHERE
    col1 NOT IN (col2, col3, col4, col5, col6) AND
    col2 NOT IN (col3, col4, col5, col6) AND
    col3 NOT IN (col4, col5, col6) AND
    col4 NOT IN (col5, col6) AND
    col5 NOT IN (col6)    -- Done as an IN just to be consistent

Answer 3

试试这个我希望这会帮助你

select 
(SELECT group_concat(DISTINCT col1) FROM table) as col1,
(SELECT group_concat(DISTINCT col2) FROM table) as col2,
(SELECT group_concat(DISTINCT col3) FROM table) as col3,
(SELECT group_concat(DISTINCT col4) FROM table) as col4

mySQL - 选择所有列都是唯一的所有记录

3 个答案: