结果一样,但是第一个要慢一些 1* select count(a.work_id),count(bb.work_id) from SA_CERT_REC_BOOK a full join SA_CERT_REC_BOOK_SN 16:53:41 SQL> /COUNT(A.WORK_ID) COUNT(BB.WORK_ID) ---------------- ----------------- 1281792 376900已用时间: 00: 01: 10.0617:03:00 SQL> select count(a.work_id),count(bb.work_id) from SA_CERT_REC_BOOK a left join SA_CERT_RE C_BOOK_SNP_ bb on a.work_id=bb.work_id union select count(a.work_id),count(bb.work_id) from SA_CERT_ REC_BOOK_SNP_ bb left join SA_CERT_REC_BOOK a on a.work_id=bb.work_id;COUNT(A.WORK_ID) COUNT(BB.WORK_ID) ---------------- ----------------- 376900 376900 1281792 376900已用时间: 00: 00: 58.07第二个效率高一些
1* select count(a.work_id),count(bb.work_id) from SA_CERT_REC_BOOK a full join SA_CERT_REC_BOOK_SN
16:53:41 SQL> /COUNT(A.WORK_ID) COUNT(BB.WORK_ID)
---------------- -----------------
1281792 376900已用时间: 00: 01: 10.0617:03:00 SQL> select count(a.work_id),count(bb.work_id) from SA_CERT_REC_BOOK a left join SA_CERT_RE
C_BOOK_SNP_ bb on a.work_id=bb.work_id union select count(a.work_id),count(bb.work_id) from SA_CERT_
REC_BOOK_SNP_ bb left join SA_CERT_REC_BOOK a on a.work_id=bb.work_id;COUNT(A.WORK_ID) COUNT(BB.WORK_ID)
---------------- -----------------
376900 376900
1281792 376900已用时间: 00: 00: 58.07第二个效率高一些
zhaokeke2004(爱拼才会赢),难道就像当然就认为第二个效率慢?