如何关联啊

[ylei2002]

str="select role_id from oa_user_role where user_id='"&user_id&'""
str="select mod_id from oa_role_mod where role_id='"&role_id&"'"

str="select mod_name,classid,pass from oa_mod where mod_id='"&mod_id&"'"

str="select name from oa_type where classid='"&classid&"'"

怎么将4个SQL语句关联啊

[yl_yz]

select 表名.字段，... from a,b,c,d where 表关联条件 and 你的where条件