2017.7.14 使用case when和group by将多条数据合并成一行，并且根据某些列的合并值做条件判断来生成最终值

参考来自：http://bbs.csdn.net/topics/390737006

1.效果演示

（1）不做处理

（2）合并多列，并对后四列的值做并集处理

2.SQL语句

（1）不做处理

 SELECT
     C .fd_tenantid AS fdTenantId,
     C .fd_resid AS fdResid,
     C .fd_res_name AS fdResName,
     C .fd_service AS fdService,
     b.fd_get AS fdGET,
     b.fd_post AS fdPOST,
     b.fd_put AS fdPUT,
     b.fd_delete AS fdDELETE
 FROM
     t_usergroup AS A
 INNER JOIN t_permission AS b ON A .fd_groupid = b.fd_groupid
 INNER JOIN t_resource AS C ON b.fd_resid = C .fd_resid
 INNER JOIN t_tenant AS d ON A .fd_tenantid = d.fd_tenantid
 WHERE
     d.fd_tenant_name = 'root'
   and a.fd_groupid  in (10026,10029)

 ORDER BY c.fd_res_name

（2）合并多列，并对后四列的值做并集处理

当列fd.get的和>=1（至少有一个真），则返回1。

 SELECT
     C .fd_tenantid AS fdTenantId,
     C .fd_resid AS fdResid,
     C .fd_res_name AS fdResName,
     C .fd_service AS fdService,
      (CASE WHEN SUM(b.fd_get) >= THEN  ELSE  END) AS fdGET,
      (CASE WHEN SUM(b.fd_post) >=1 THEN 1 ELSE 0 END) AS fdPOST,
      (CASE WHEN SUM(b.fd_put) >=1 THEN 1 ELSE 0 END) AS fdPUT,
      (CASE WHEN SUM(b.fd_delete) >=1 THEN 1 ELSE 0 END) AS fdDELETE
 FROM
     t_usergroup AS A
 INNER JOIN t_permission AS b ON A .fd_groupid = b.fd_groupid
 INNER JOIN t_resource AS C ON b.fd_resid = C .fd_resid
 INNER JOIN t_tenant AS d ON A .fd_tenantid = d.fd_tenantid
 WHERE
     d.fd_tenant_name = 'root'
   and a.fd_groupid  in (10026,10029)

 GROUP BY 
    d.fd_tenantid,c.fd_resid,c.fd_service
 ORDER BY c.fd_res_name