select
vtiger_users.id,
vtiger_users.user_name,
vtiger_role.rolename
FROM
vtiger_users
inner join vtiger_role
inner join vtiger_user2role
on vtiger_users.id = vtiger_user2role.userid
and vtiger_user2role.roleid = vtiger_role.roleid
select
字段1,字段2,字段3
from
表1
inner join 表2
inner join 表3 on
表1.字段 = 表2.字段
and 表2.字段 = 表3.字段