用sql比较两个数据库是否一致

select case when a.cnt = b.cnt then "两个库结构一致"
when a.cnt <> b.cnt then "两个库结构不一致" end
from (select count(*) as cnt
from dba_tab_columns t1, dba_tab_columns@lnk_db2 t2
where t1.owner = "TAOBAO"
and t1.owner = t2.owner
and t1.table_name = t2.table_name
and t1.column_name = t2.column_name
and t1.data_type = t2.data_type
and t1.data_length = t2.data_length
and t1.nullable = t2.nullable
and nvl(t1.data_precision, 0) = nvl(t2.data_precision, 0)
and nvl(t1.data_scale, 0) = nvl(t2.data_scale, 0)) a,
(select count(*) as cnt
from dba_tab_columns
where owner = "TAOBAO") b