{"id":111,"date":"2010-12-28T23:24:49","date_gmt":"2010-12-28T15:24:49","guid":{"rendered":"http:\/\/www.royalwzy.com\/?p=111"},"modified":"2013-12-30T10:58:18","modified_gmt":"2013-12-30T02:58:18","slug":"delete-truncate-drop-%e7%9a%84%e5%8c%ba%e5%88%ab","status":"publish","type":"post","link":"http:\/\/www.royalwzy.com\/?p=111","title":{"rendered":"DELETE, TRUNCATE, DROP \u7684\u533a\u522b"},"content":{"rendered":"<p>1. delete\/truncate\u00a0\u53ea\u5220\u9664\u6570\u636e\u4e0d\u5220\u9664\u8868,\u7d22\u5f15\u7684\u7ed3\u6784. drop\u00a0\u5c06\u5220\u9664\u8868\u7684\u7ed3\u6784\u88ab\u4f9d\u8d56\u7684index\/constrain\/trigger,\u4f9d\u8d56\u4e8e\u8be5\u8868\u7684\u00a0procedure\/function\u00a0\u5c06\u4fdd\u7559,\u4f46\u662f\u53d8\u4e3a\u00a0invalid\u00a0\u72b6\u6001<\/p>\n<p>2. delete\u00a0\u662f\u00a0dml,\u5199\u00a0rollback segement,\u53ef\u56de\u6eda,\u901f\u5ea6\u6162,\u4e8b\u52a1\u63d0\u4ea4\u4e4b\u540e\u624d\u751f\u6548.\u5728\u00a09i\u00a0\u6ee1\u8db3undo_retention\u00a0\u6761\u4ef6\u4e0b\u53ef\u4f7f\u7528\u00a0flashback.\u4e00\u6b21\u6027\u5927\u6279\u91cf\u6570\u636e\u7684\u00a0delete\u00a0\u53ef\u80fd\u5bfc\u81f4\u56de\u6eda\u6bb5\u6025\u5267\u6269\u5c55\u4ece\u800c\u5f71\u54cd\u5230\u6570\u636e\u5e93,\u614e\u7528.\u89e6\u53d1\u00a0trigger. truncate\/drop\u00a0\u662f\u00a0ddl,\u9690\u5f0f\u63d0\u4ea4,\u4e0d\u5199\u00a0rollback segment,\u4e0d\u80fd\u56de\u6eda,\u901f\u5ea6\u5feb.9i\u4e0d\u80fd\u4f7f\u7528\u00a0flashback.\u4e0d\u89e6\u53d1\u00a0trigger<\/p>\n<p>3. delete\u00a0\u4e0d\u5f71\u54cd\u8868\u6240\u5360\u7528\u7684\u00a0extent, HWM\u00a0\u4fdd\u6301\u539f\u4f4d\u7f6e\u4e0d\u52a8,\u5373\u4f7f\u5220\u9664\u7684\u662f\u6700\u9760\u8fd1\u00a0HWM\u00a0\u7684\u6570\u636e.delete\u00a0\u5176\u5b9e\u4e5f\u53ef\u4ee5\u91ca\u653e\u7a7a\u95f4,\u4f46\u662f\u4e0d\u964d\u4f4e\u00a0HWM, delete\u00a0\u540e\u00a0block\u00a0\u7684\u7a7a\u95f2\u7a7a\u95f4\u8fbe\u5230\u00a0pct_used,\u5c31\u53ef\u4ee5\u91cd\u7528. truncate\u00a0\u7f3a\u7701\u60c5\u51b5\u4e0b\u5c06\u7a7a\u95f4(\u8868\u548c\u7d22\u5f15)\u91ca\u653e\u5230\u00a0minextents\u00a0\u4e2a\u00a0extent,\u9664\u975e\u4f7f\u7528\u00a0reuse storage.truncate\u00a0\u4f1a\u5c06\u9ad8\u6c34\u7ebf\u590d\u4f4d(\u56de\u5230\u6700\u5f00\u59cb). drop\u00a0\u5c06\u8868\u6240\u5360\u7528\u7684\u7a7a\u95f4\u5168\u90e8\u91ca\u653e,segment\u00a0\u4e0d\u5b58\u5728,\u65e0\u6240\u8c13\u00a0HWM\u00a0\u7684\u6982\u5ff5<\/p>\n<p>4. truncate\/drop\u00a0\u7684\u5bf9\u8c61\u5fc5\u987b\u662f\u672c\u6a21\u5f0f\u4e0b\u7684,\u6216\u8005\u88ab\u6388\u4e88\u00a0drop any table\u00a0\u7684\u6743\u9650,\u4f46\u00a0drop any table\u00a0\u6743\u9650\u4e0d\u80fd\u00a0truncate\/drop sys\u00a0\u7684\u8868. delete\u00a0\u7684\u5bf9\u8c61\u5fc5\u987b\u662f\u672c\u6a21\u5f0f\u4e0b\u7684,\u6216\u8005\u88ab\u6388\u4e88\u00a0delete on SCHEMA.table\u6216\u00a0delete any table\u00a0\u7684\u6743\u9650,\u4f46\u00a0delete any table\u00a0\u6743\u9650\u4e0d\u80fd\u00a0delete sys\u00a0\u7684\u8868<\/p>\n<p>5.\u00a0\u4e0d\u80fd\u00a0truncate\u00a0\u4e00\u4e2a\u5e26\u6709\u00a0enable\u00a0\u5916\u952e\u7684\u8868,\u4e0d\u7ba1\u8868\u91cc\u6709\u6ca1\u6709\u6570\u636e,\u5982\u679c\u8981\u00a0truncate,\u9996\u5148\u8981\u00a0disable\u00a0\u5916\u952e\u6216\u8005\u5220\u9664\u5916\u952e(drop\u00a0\u5916\u952e\u7684\u8868\u80af\u5b9a\u662f\u5220\u9664\u4e86\u5916\u952e).\u4e0d\u80fd\u00a0drop\u00a0\u4e00\u4e2a\u5e26\u6709\u00a0enable\u00a0\u5916\u952e\u7684\u8868,\u4e0d\u7ba1\u8868\u91cc\u6709\u6ca1\u6709\u6570\u636e,\u5982\u679c\u8981\u00a0drop,\u9996\u5148\u8981\u5220\u9664\u5916\u952e,\u6216\u8005\u76f4\u63a5\u7528\u00a0drop table TABLE_NAME cascade constraints;\u00a0\u7ea7\u8054\u5220\u9664\u5916\u952e. delete\u00a0\u53ef\u4ee5.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. delete\/truncate\u00a0\u53ea\u5220\u9664\u6570\u636e\u4e0d\u5220\u9664\u8868,\u7d22\u5f15\u7684\u7ed3\u6784. drop\u00a0\u5c06\u5220\u9664\u8868\u7684\u7ed3\u6784\u88ab\u4f9d\u8d56\u7684ind [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[34,2],"class_list":["post-111","post","type-post","status-publish","format-standard","hentry","category-oracle","tag-oracle","tag-oracle_basics"],"_links":{"self":[{"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=\/wp\/v2\/posts\/111","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=111"}],"version-history":[{"count":0,"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=\/wp\/v2\/posts\/111\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=111"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=111"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.royalwzy.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}