将列数据转换为由逗号分隔的行数据，并在MySql中逐列分隔

Question

我想将列转换为以逗号分隔的单行。

当前表：

main_cat | sub_cat |
--------------------
main 1   | sub 1   |
main 1   | sub 2   |
main 2   | sub 2   |
main 2   | sub 3   |
main 3   | sub 1   |

预期表

group_main             | main 1       | main 2     | main 3 |
-------------------------------------------------------------
main 1, main 2, main 3 | sub 1, sub 2 |sub 2, sub 3|sub 1   |

我尝试GROUP_CONCAT但未获得准确的输出

Answer 1

您可以使用条件聚合：

select group_concat(distinct main_cat order by main_cat) as group_main,
       group_concat(case when main_cat = 'main 1' then sub_cat end order by sub_cat) as main_1,
       group_concat(case when main_cat = 'main 2' then sub_cat end order by sub_cat) as main_2,
       group_concat(case when main_cat = 'main 3' then sub_cat end order by sub_cat) as main_3
from t;