sql case when 多条件

when

 'ChangeProductName'=

  case  --联名借姓名

   --when  a.ChangeProductName is not null   then (substring(a.ChangeProductName,0,charindex(',', ChangeProductName)))   --联名借姓名

   --when  a.ChangeProductName <> '' then (substring(a.ChangeProductName,0,charindex(',', ChangeProductName))) 

   when  (a.ChangeProductName is not null and a.ChangeProductName <> '')   then substring(a.ChangeProductName,0,charindex(',', ChangeProductName))   --联名借姓名

  end,