多列合并一类,去重

 SELECT
      GROUP_CONCAT( DISTINCT ( con_name ) ) con_name 
FROM

table

table

  --查询用户对应的角色，变将角色名称合并成一列显示

  --listagg(roles.name,'-')within  group  (order by users.id desc ) as roleName

  --group by users.id,users.realname,users.username

  select 

    users.id,

    users.realname,

    users.username,

    listagg(roles.name,'-')within  group  (order by users.id desc ) as roleName

  from sys_users users 

  inner join sys_users_roles usersRoles on users.id = usersRoles.User_Id

  inner join sys_roles roles on roles.id = usersRoles.role_id

  where 1=1  

  group by users.id,users.realname,users.username

  order by id desc; 

oralce中如何将多列合成一行，并用分隔符来分割,以下是SQL:

select  listagg(serial_number, ‘’’,’’’)  within group (order by serial_number) ||’’’’ from table  where  rownum<5;