{"id":1425,"date":"2018-04-23T10:02:29","date_gmt":"2018-04-23T02:02:29","guid":{"rendered":"http:\/\/www.821121.com\/?p=1425"},"modified":"2021-03-02T10:51:40","modified_gmt":"2021-03-02T02:51:40","slug":"%e9%97%aa%e5%9b%9e%e6%9f%a5%e8%af%a2%ef%bc%88flashback-query%ef%bc%89%e6%a8%a1%e6%8b%9f%e6%b5%8b%e8%af%95","status":"publish","type":"post","link":"http:\/\/www.821121.com\/?p=1425","title":{"rendered":"\u95ea\u56de\u67e5\u8be2\uff08flashback query\uff09\u6a21\u62df\u6d4b\u8bd5"},"content":{"rendered":"<pre><code class=\"language-sql\">Flashback query\u662f\u6700\u57fa\u672c\u7684\u95ea\u56de\u529f\u80fd\uff0c\u76f4\u63a5\u5229\u7528\u56de\u6eda\u6bb5\u4e2d\u7684\u65e7\u6570\u636e\u6784\u9020\u67d0\u4e00\u4e2a\u65f6\u523b\u7684\u4e00\u81f4\u6027\u6570\u636e\u7248\u672c\u3002\u53ea\u9002\u5408\u5355\u4e2a\u8868\u6570\u636e\u6062\u590d\u3002\u5bf9\u4e8b\u52a1\u4e2d\u76f8\u5173\u591a\u8868\u6570\u636e\u6062\u590d\u4e0d\u9002\u5408\uff0c\u65e0\u6cd5\u786e\u4fdd\u76f8\u5173\u6570\u636e\u7684\u53c2\u7167\u5b8c\u6574\u6027\u3002Flashback query\u4e0d\u9700\u8981\u4f7f\u7528resetlogs\u6253\u5f00\u6570\u636e\u5e93\u3002\u95ea\u56de\u67e5\u8be2\u8ba9\u4f60\u80fd\u591f\u770b\u5230\u8fc7\u53bb\u67d0\u4e2a\u65f6\u95f4\u7684\u7684\u6570\u636e\u3002\u80fd\u591f\u8ba9\u4f60\u67e5\u770b\u548c\u91cd\u6784\u4ee5\u4e3a\u610f\u5916\u88ab\u5220\u9664\u6216\u8005\u8be5\u8868\u7684\u6570\u636e\u3002\u4f60\u53ef\u4ee5\u6839\u636eSCN\u53f7\u548c\u5177\u4f53\u65f6\u95f4\u8fdb\u884c\u6570\u636e\u5e93\u67e5\u8be2\u3002\u53c2\u6570undo_retention \u8868\u660e\u5728\u56de\u6eda\u6bb5\u4e2d\u65e7\u7684\u4fe1\u606f\u88ab\u8986\u76d6\u4e4b\u524d\u4fdd\u7559\u7684\u65f6\u95f4\u3002\u901a\u8fc7\u4f7f\u7528AS OF\u5b57\u53e5\uff0c\u4f60\u53ef\u4ee5\u67e5\u8be2\u4e00\u4e2a\u8868\u4e2d\u4e0d\u540c\u65f6\u6bb5\u7684\u5feb\u7167\u3002\u6307\u5b9aAS OF\u80fd\u591f\u901a\u8fc7\u6307\u5b9a\u7684SCN\u6216\u8005\u65f6\u95f4\u6233\u6765\u83b7\u53d6\u6240\u6709\u884c\u7684\u5355\u4e2a\u7248\u672c\uff0c\u5982\u679c\u4f60\u6307\u5b9aSCN\uff0c\u5219\u540e\u9762\u5fc5\u987b\u8ddf\u6570\u5b57\uff0c\u5982\u679c\u4f60\u6307\u5b9atimestamp\uff0c\u5219\u540e\u9762\u5fc5\u987b\u6307\u5b9a\u4e00\u4e2a\u5177\u4f53\u65f6\u95f4\uff0cOralce\u6570\u636e\u4f1a\u8fd4\u56de\u5728\u8be5\u65f6\u95f4\u70b9\u6216\u8005SCN\u53f7\u65f6\u7684\u6570\u636e<\/code><\/pre>\n<pre><code class=\"language-sql\">\u6839\u636eSCN\u7684\u95ea\u56de\u67e5\u8be2\uff1a\n1\u3001\u521d\u59cb\u5316\u6570\u636e\nSQL&gt; create table t(a number,b number);\nTable created.\nSQL&gt; insert into t values(1,1);\n1 row created.\nSQL&gt; insert into t values(2,2);\n1 row created.\nSQL&gt; insert into t values(3,3);\n1 row created.\nSQL&gt; commit;\nCommit complete.\n2\u3001\u67e5\u8be2\u5f53\u524d\u65f6\u95f4\u3001\u5f53\u524dSCN\u53f7\nSQL&gt; alter session set nls_date_format=&#039;yyyymmdd hh24:mi:ss&#039;;\nSession altered.\nSQL&gt; select sysdate from dual; ---\u83b7\u53d6\u5f53\u524d\u65f6\u95f4\nSYSDATE\n-----------------\n20210121 14:56:40\nSQL&gt; select dbms_flashback.get_system_change_number from dual; ---\u83b7\u53d6\u5f53\u524dSCN\nGET_SYSTEM_CHANGE_NUMBER\n------------------------\n                 2166044\n\n3\u3001\u5220\u9664\u90e8\u5206\u6570\u636e\nSQL&gt; delete from t where b=3;\n1 row deleted.\nSQL&gt; commit;\nCommit complete.\n4\u3001\u6839\u636eSCN\u6216\u8005\u65f6\u95f4\u8fdb\u884c\u95ea\u56de\u67e5\u8be2\nSQL&gt; select * from t;\n         A          B\n---------- ----------\n         1          1\n         2          2\nSQL&gt; select * from t as of scn 2166044;  ---\u6839\u636eSCN\u53f7\u5f97\u5230\u5728\u8be5SCN\u53f7\u65f6\u7684\u6570\u636e\u60c5\u51b5\n         A          B\n---------- ----------\n         1          1\n         2          2\n         3          3\nSQL&gt; select * from t as of timestamp to_timestamp(&#039;20210121 14:56:40&#039;,&#039;yyyymmdd hh24:mi:ss&#039;); --\u5f97\u5230\u5177\u4f53\u65f6\u95f4\u70b9\u7684\u6570\u636e\n         A          B\n---------- ----------\n         1          1\n         2          2\n         3          3\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Flashback query\u662f\u6700\u57fa\u672c\u7684\u95ea\u56de\u529f\u80fd\uff0c<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18],"tags":[],"class_list":["post-1425","post","type-post","status-publish","format-standard","hentry","category-oracle-11g"],"_links":{"self":[{"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/posts\/1425","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.821121.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1425"}],"version-history":[{"count":1,"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/posts\/1425\/revisions"}],"predecessor-version":[{"id":1426,"href":"http:\/\/www.821121.com\/index.php?rest_route=\/wp\/v2\/posts\/1425\/revisions\/1426"}],"wp:attachment":[{"href":"http:\/\/www.821121.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1425"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.821121.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1425"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.821121.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1425"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}