Question

我有数据。

   A,   STATUS,  P
   A1,    1,     P1
   A1,    1,     P2
   A1,    1,     P3
   A2,    1,     P3
   A2,    1,     P4
   A2,    1,     P5
   A3,    0,     NULL

我想要结果相同

   P,   A1,  A2,  A3
   P1,  1,   0,   0
   P2,  1,   0,   0
   P3,  1,   1,   0
   P4,  0,   1,   0
   P5,  0,   1,   0

我怎么能用mysql查询呢？

Answer 1

试试这个;）

select
    `P`,
    max(if(`A` = 'A1', `STATUS`, 0)) as `A1`,
    max(if(`A` = 'A2', `STATUS`, 0)) as `A2`,
    max(if(`A` = 'A3', `STATUS`, 0)) as `A3`
from table1
where `P` IS NOT NULL
group by `P`

DEMO HERE

<强>编辑：

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'MAX(IF(`A` = ''',
      `A`,
      ''', `STATUS`, 0)) AS ',
      `A`
    )
  ) INTO @sql
FROM table1;
SET @sql = CONCAT('SELECT `P`, ', @sql, ' FROM table1 WHERE `P` IS NOT NULL GROUP BY `P`');

PREPARE stmt FROM @sql;
EXECUTE stmt;

<强> DEMO HERE

Answer 2

假设您知道潜在列的最大数量，则可以使用conditional aggregation来转移结果：

select p, 
       max(case when a = 'A1' then status else 0 end) a1,
       max(case when a = 'A2' then status else 0 end) a2,
       max(case when a = 'A3' then status else 0 end) a3
from yourtable
group by p

SQL Fiddle Demo

如果您不知道潜在列的数量，则需要使用dynamic sql代替。

MySQL数据透视数据

2 个答案: