MySql 计算分组字段百分比并显示在一行

Question

+--------+--------+--------+------------+
| line | field1 | count|
| x |    a | 2 |
| x |    b | 2 |
| x |    c | 1 |
| y |    a | 1 |
| y |    b | 1 |
| y |    c | 1 |
| y |    d|  1 |

如您所见，上表表示的行是分组字段，我尝试获取类似或类似的查询结果：

+--------+--------+--------+------------+
| line | field1-percentage|
| x |  a-%40,b-%40,c-%20 |
| y |  a-%25,b-%25,c-%20 |

Answer 1

列名已更改（count 为 Reserved word）。

对于 MySQL 8+ 使用

WITH cte AS ( SELECT category, entity, SUM(amount) amount
              FROM test
              GROUP BY category, entity WITH ROLLUP )
SELECT category, GROUP_CONCAT(t1.entity, '-%', ROUND(100 * t1.amount / t2.amount)) percentage
FROM cte t1
JOIN cte t2 USING (category)
WHERE t2.entity IS NULL
GROUP BY category;

对于 MySQL 5.x 使用：

SELECT category, GROUP_CONCAT(t1.entity, '-%', ROUND(100 * t1.amount / t2.amount)) percentage
FROM ( SELECT category, entity, SUM(amount) amount
       FROM test
       GROUP BY category, entity ) t1
JOIN ( SELECT category, SUM(amount) amount
       FROM test
       GROUP BY category ) t2 USING (category)
GROUP BY category;

fiddle