如何进行大量的数据比对

candy84528

如何进行数据比对
用access 能不能提供运行速度比较快的SQL

有一组SQL 能不能帮我解释下 为什么这么写 以及 这么写 会漏查出什么？

SELECT MIN(FILE) AS RESULT, aaa,bbb from

[
SELECT "AAAAA" AS FILE, A.aaa A.bbb from AODS AS A
Union All
SELECT "BBBBB" AS FILE, B.aaa , B.bbb from MCCDSS AS B
]. AS TEMP


GROUP BY TEMP.aaa,TEMP.bbb

HAVING COUNT(*) = 1

ORDER BY TEMP.state_cd