使用查询按project_id列出

Question

我有一个包含以下值的表：

id    employee_id    project_id
1     1              1
2     2              1
3     3              1
4     4              1

我如何按project_id列出？使用mysql查询？

project_id        employee_id        employee_id        employee_id        employee_id
1                 1                  2                  3                  4

Answer 1

尝试以下查询 -

SELECT project_id ,SUBSTRING_INDEX(GROUP_CONCAT(employee_id),',',1) AS employee_id1,SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(employee_id),',',2),',',-1) AS employee_id2, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(employee_id),',',3),',',-1) AS employee_id3, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(employee_id),',',4),',',-1) AS employee_id4 FROM my_table GROUP BY project_id;

Answer 2

  

SELECT project_id，GROUP_CONCAT（employee_id）FROM Table GROUP BY project_id;

可以考虑.. ??