select FileCode from p1.p_user
UNION all
select FileCode from p2.p_user
UNION all
select FileCode from p3.p_user
UNION all
select FileCode from p4.p_user
UNION all
select FileCode from p5.p_user
UNION all
select FileCode from p6.p_user
select FileCode from p7.p_user
UNION all
select FileCode from p8.p_user
p*库名
p_user表名