Question

任何想法如何在MySQL中实现这一点：

有数据：

Item, class, x, y, z, A, B, C
1,     new,  1, 0, 0, 1, 1, 0
2,     red,  1, 1, 0, 0, 1, 1
3,     new,  0, 0, 1, 1, 0, 1

（如果这是一个更容易的出发点，数据也会采用1, new, X, AB或2, red, XY, BC格式。）

需要：

1, new, X, A
1, new, X, B
2, red, X, B
2, red, X, C
2, red, Y, B
2, red, Y, C
3, new, Z, A
3, new, Z, C

任何帮助都会非常受欢迎。感谢。

Answer 1

尝试使用嵌套的case语句，如下所示：

 select t.item, t.class, 
 Case when t.X = 1 then 'X' else
      case when t.Y = 1 then 'Y' else
           case when t.Z = 1 then 'Z' end
      end
 end ,
 Case when t.A = 1 then 'A' else 
      case when t.B = 1 then 'B' else
           case when t.C = 1 then 'C' end
      end
 end
 from YourTableName t

Answer 2

对于少数“xyzABC ...”列，您可以使用：

SELECT item,class,'x','A' FROM `test_pivot` WHERE x=1 AND a=1 UNION
SELECT item,class,'x','B' FROM `test_pivot` WHERE x=1 AND b=1 UNION
SELECT item,class,'x','C' FROM `test_pivot` WHERE x=1 AND c=1 UNION
SELECT item,class,'y','A' FROM `test_pivot` WHERE y=1 AND a=1 UNION
SELECT item,class,'y','B' FROM `test_pivot` WHERE y=1 AND b=1 UNION
SELECT item,class,'y','C' FROM `test_pivot` WHERE y=1 AND c=1 UNION
SELECT item,class,'z','A' FROM `test_pivot` WHERE z=1 AND a=1 UNION
SELECT item,class,'z','B' FROM `test_pivot` WHERE z=1 AND b=1 UNION
SELECT item,class,'z','C' FROM `test_pivot` WHERE z=1 AND c=1

MySQL Transpose（Pivot）变体：将列的所有组合移动到新行中

2 个答案: