oracle 查询函数wm_concat，decode，COALESCE

wm_concat(to_char(u.user_name)) as user_name,       ----多条数据合并在一行显示
wm_concat(to_char(u.id)) as org_user_id,                     ----多条数据合并在一行显示
decode(bob.id,'','个体',sd.name) as business_type,       ----  id 为空就显示类型为个体，不为空就显示相对应的类型
COALESCE(bob.legal_person,e.manage_name) as legal_person,   ---- egal_person, manage_name  显示不为空的那个那个字段 作为一个字段显示