{"id":1241,"date":"2015-06-02T23:33:12","date_gmt":"2015-06-02T15:33:12","guid":{"rendered":"http:\/\/coderbee.net\/?p=1241"},"modified":"2015-07-13T22:44:14","modified_gmt":"2015-07-13T14:44:14","slug":"%e3%80%8a%e5%9f%ba%e4%ba%8e-oracle-%e7%9a%84-sql-%e4%bc%98%e5%8c%96%e3%80%8b%e7%ac%94%e8%ae%b0-%e7%ac%ac%e4%ba%94%e7%ab%a0-oracle-%e9%87%8c%e7%bb%9f%e8%ae%a1%e4%bf%a1%e6%81%af","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/db\/20150602\/1241","title":{"rendered":"\u300a\u57fa\u4e8e Oracle \u7684 SQL \u4f18\u5316\u300b\u7b14\u8bb0 \u7b2c\u4e94\u7ae0 Oracle \u91cc\u7edf\u8ba1\u4fe1\u606f"},"content":{"rendered":"<p>CBO \u662f\u57fa\u4e8e\u5bf9\u5404\u79cd\u4e0d\u540c\u6267\u884c\u8def\u5f84\u6210\u672c\u7684\u8ba1\u7b97\uff0c\u6bd4\u8f83\u5e76\u9009\u53d6\u6210\u672c\u503c\u6700\u5c0f\u7684\u6267\u884c\u8def\u5f84\u6765\u4f5c\u4e3a\u76ee\u6807 SQL \u7684\u6267\u884c\u8ba1\u5212\u7684\uff1b\u800c\u6210\u672c\u503c\u7684\u8ba1\u7b97\u5219\u662f\u6839\u636e\u76ee\u6807 SQL \u6240\u6d89\u53ca\u7684\u8868\u3001\u7d22\u5f15\u3001\u5217\u7b49\u76f8\u5173\u5bf9\u8c61\u7684\u7edf\u8ba1\u4fe1\u606f\uff0c\u8fd0\u7528 CBO \u56fa\u6709\u7684\u6210\u672c\u503c\u8ba1\u7b97\u516c\u5f0f\u8ba1\u7b97\u51fa\u6765\u7684\u3002\u6240\u4ee5\uff0c\u5bf9\u7edf\u8ba1\u4fe1\u606f\u7684\u4e86\u89e3\u6210\u4e86\u7406\u89e3 CBO\u3001\u7406\u89e3\u6267\u884c\u8ba1\u5212\u7684\u5173\u952e\u3002<\/p>\n<p>Oracle \u6570\u636e\u5e93\u91cc\u7684\u7edf\u8ba1\u4fe1\u606f\u5206\u4e3a\u516d\u79cd\u7c7b\u578b\uff0c\u5305\u542b\u5bf9\u5e94\u7684\u5bf9\u8c61\u7684\u4fe1\u606f\uff0c\u7ef4\u5ea6\u4e0d\u540c\uff1a<\/p>\n<ul>\n<li>\u8868\u7684\u7edf\u8ba1\u4fe1\u606f\uff1a\u5178\u578b\u7684\u7ef4\u5ea6\u6709 \u8bb0\u5f55\u6570\u3001\u8868\u5757\uff08\u8868\u91cc\u7684\u6570\u636e\u5757\uff09\u7684\u6570\u91cf\u3001\u5e73\u5747\u884c\u957f\u5ea6\u7b49\u3002<\/li>\n<li>\u7d22\u5f15\u7684\u7edf\u8ba1\u4fe1\u606f\uff1a\u5178\u578b\u7684\u7ef4\u5ea6\u6709 \u7d22\u5f15\u7684\u5c42\u7ea7\u3001\u53f6\u5b50\u5757\u7684\u6570\u91cf\u3001\u805a\u65cf\u56e0\u5b50\u7b49\u3002<\/li>\n<li>\u5217\u7684\u7edf\u8ba1\u4fe1\u606f\uff1a\u5178\u578b\u7684\u7ef4\u5ea6\u6709  \u5217\u7684 distinct \u503c\u7684\u6570\u91cf\u3001\u5217\u7684 null \u503c\u7684\u6570\u91cf\u3001\u5217\u7684\u6700\u5c0f\u503c\u3001\u5217\u7684\u6700\u5927\u503c\u4ee5\u53ca\u76f4\u65b9\u56fe\u7b49\u3002<\/li>\n<li>\u7cfb\u7edf\u7edf\u8ba1\u4fe1\u606f\uff1a\u6240\u5728\u6570\u636e\u5e93\u670d\u52a1\u5668\u7684\u7cfb\u7edf\u5904\u7406\u80fd\u529b\uff0c\u5305\u542b\u6765 CPU \u548c I\/O \u8fd9\u4e24\u4e2a\u7ef4\u5ea6\uff0c\u501f\u52a9\u4e8e\u7cfb\u7edf\u7edf\u8ba1\u4fe1\u606f\uff0cOracle \u53ef\u4ee5\u77e5\u9053\u76ee\u6807\u6570\u636e\u5e93\u670d\u52a1\u5668\u7684\u5b9e\u9645\u5904\u7406\u80fd\u529b\u3002<\/li>\n<li>\u6570\u636e\u5b57\u5178\u7edf\u8ba1\u4fe1\u606f\uff1a\u63cf\u8ff0 Oracle \u6570\u636e\u5e93\u91cc\u7684\u6570\u636e\u5b57\u5178\u57fa\u8868\uff08\u5982 <code>TAB$<\/code>\u3001<code>IND$<\/code>  \u7b49\uff09\u6570\u636e\u5b57\u5178\u57fa\u8868\u4e0a\u7684\u7d22\u5f15\uff0c\u4ee5\u53ca\u8fd9\u4e9b\u6570\u636e\u5b57\u5178\u57fa\u8868\u7684\u5217\u7684\u8be6\u7ec6\u4fe1\u606f\uff0c\u4e0e\u666e\u901a\u8868\u3001\u7d22\u5f15\u3001\u5217\u7684\u7edf\u8ba1\u4fe1\u606f\u6ca1\u6709\u672c\u8d28\u533a\u522b\u3002<\/li>\n<li>\u5185\u90e8\u5bf9\u8c61\u7edf\u8ba1\u4fe1\u606f\uff1a\u63cf\u8ff0 Oracle \u6570\u636e\u5e93\u91cc\u7684\u5185\u90e8\u8868\uff08\u5982 <code>X$<\/code> \u7cfb\u5217\u8868\uff0c\u5176\u5b9e\u53ea\u662f Oracle \u81ea\u5b9a\u4e49\u7684\u5185\u5b58\u7ed3\u6784\uff09\u7684\u4fe1\u606f\u4fe1\u606f\uff0c\u5e76\u4e0d\u5360\u7528\u5b9e\u9645\u7684\u7269\u7406\u5b58\u50a8\u7a7a\u95f4\u3002<\/li>\n<\/ul>\n<p>\u53ef\u4ee5\u7528 <code>ANALYZE<\/code>  \u547d\u4ee4\uff08\u53ea\u80fd\u6536\u96c6\u524d\u56db\u79cd\uff0c\u4e14\u4e0d\u80fd\u5e76\u884c\u6536\u96c6\uff09\u6216 <code>DBMS_STATS<\/code> \u5305\u6765\u6536\u96c6\u7edf\u8ba1\u4fe1\u606f\uff0c<\/p>\n<p><!--more--><\/p>\n<p>\u5728\u5bfc\u5165\u5927\u91cf\u6570\u636e\u540e\u5e94\u53ca\u65f6\u6536\u96c6\u7edf\u8ba1\u4fe1\u606f\u540e\u624d\u8fdb\u884c\u76f8\u5173\u7684\u540e\u7eed\u4e1a\u52a1\u64cd\u4f5c\uff08\u5305\u62ec\u67e5\u8be2\u548c\u4fee\u6539\uff09\uff0c\u5426\u5219\u53ef\u80fd\u4f1a\u7531\u4e8e\u5b9e\u9645\u6570\u636e\u91cf\u548c\u7edf\u8ba1\u4fe1\u606f\u91cc\u8bb0\u5f55\u7684\u6570\u636e\u91cf\u5b58\u5728\u5de8\u5927\u5dee\u5f02\u800c\u5bfc\u81f4 CBO \u9009\u62e9\u9519\u8bef\u7684\u6267\u884c\u8ba1\u5212\u3002<br \/>\n\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u8e29\u8fc7\u5751\uff0c\u7b2c\u4e00\u6b21\u5728 Oracle \u6570\u636e\u5e93\u91cc\u628a\u73b0\u6709\u7684\u4e1a\u52a1\u8868\u8f6c\u4e3a\u5206\u533a\u8868\u65f6\uff0c\u91c7\u7528\u7684\u662f\u5efa\u7acb\u65b0\u7684\u8868\uff0c\u7136\u540e\u628a\u6570\u636e\u5bfc\u8fc7\u53bb\uff0c\u7d22\u5f15\u5efa\u597d\uff0c\u5207\u4e86\u8868\u540d\uff0c\u5e94\u7528\u8d77\u6765\u540e\u6162\u5f97\u4e0d\u5f97\u4e86\uff0c\u4e00\u770b\u6267\u884c\u8ba1\u5212\uff0c\u5404\u79cd\u5168\u8868\u626b\u63cf\uff0c\u54ea\u6015\u552f\u4e00\u6027\u7684\u7d22\u5f15\u90fd\u6240\u8d70\u7d22\u5f15\u5168\u626b\u63cf\uff0c\u5c31\u662f\u56e0\u4e3a\u7edf\u8ba1\u4fe1\u606f\u6ca1\u6709\u3002<\/p>\n<h3>\u805a\u65cf\u56e0\u5b50\u7684\u542b\u4e49\u53ca\u91cd\u8981\u6027<\/h3>\n<p>\u5728 Oracle \u6570\u636e\u5e93\u91cc\uff0c\u805a\u65cf\u56e0\u5b50\u6240\u6307\u6309\u7167\u7d22\u5f15\u952e\u503c\u6392\u5e8f\u7684\u7d22\u5f15\u884c\u548c\u5b58\u50a8\u4e8e\u5bf9\u5e94\u8868\u4e2d\u7684\u6570\u636e\u884c\u7684\u5b58\u50a8\u987a\u5e8f\u7684\u76f8\u4f3c\u7a0b\u5ea6\u3002<\/p>\n<p>Oracle \u6309\u7167\u5982\u4e0b\u65b9\u6cd5\u8ba1\u7b97\u805a\u65cf\u56e0\u5b50\u7684\u503c\uff1a<\/p>\n<ol>\n<li>\u805a\u65cf\u56e0\u5b50\u7684\u521d\u59cb\u503c\u4e3a 1\u3002<\/li>\n<li>Oracle \u9996\u5148\u5b9a\u4f4d\u5230\u76ee\u6807\u7d22\u5f15\u5904\u4e8e\u6700\u5de6\u8fb9\u7684\u53f6\u5b50\u5757\u3002<\/li>\n<li>\u4ece\u6700\u5de6\u8fb9\u7684\u53f6\u5b50\u5757\u7684\u7b2c\u4e00\u4e2a\u7d22\u5f15\u952e\u503c\u6240\u5728\u7684\u7d22\u5f15\u884c\u5f00\u59cb\u987a\u5e8f\u626b\u63cf\uff0c\u5728\u987a\u5e8f\u626b\u63cf\u7684\u8fc7\u7a0b\u4e2d\uff0cOracle \u4f1a\u6bd4\u5bf9\u5f53\u524d\u7d22\u5f15\u884c\u7684 rowid \u548c\u5b83\u4e4b\u524d\u7684\u90a3\u4e2a\u7d22\u5f15\u884c\u7684 rowid\uff0c<br \/>\n\u5982\u679c\u8fd9\u4e24\u4e2a rowid \u5e76\u4e0d\u662f\u6307\u5411\u540c\u4e00\u4e2a\u8868\u5757\uff08\u4e0d\u9700\u8981\u56de\u8868\uff09\uff0c\u90a3\u4e48 Oracle \u5c31\u5c06\u805a\u65cf\u56e0\u5b50\u7684\u5f53\u524d\u503c\u9012\u589e 1 \uff0c\u5426\u5219\u4e0d\u53d8\u3002<\/li>\n<li>\u91cd\u590d\u6b65\u9aa4 3 \u76f4\u81f3\u987a\u5e8f\u626b\u63cf\u5b8c\u76ee\u6807\u7d22\u5f15\u6240\u6709\u53f6\u5b50\u5757\u91cc\u7684\u6240\u6709\u7d22\u5f15\u884c\u3002<\/li>\n<li>\u626b\u63cf\u5b8c\u6210\u540e\uff0c\u805a\u65cf\u56e0\u5b50\u7684\u5f53\u524d\u503c\u5c31\u662f\u7d22\u5f15\u7edf\u8ba1\u4fe1\u606f\u4e2d\u7684 CLUSTERING_FACTOR\uff0cOracle \u4f1a\u5c06\u5176\u5b58\u5728\u6570\u636e\u5b57\u5178\u91cc\u3002<\/li>\n<\/ol>\n<p>\u805a\u65cf\u56e0\u5b50\u4f4e\u610f\u5473\u7740\u8d70\u7d22\u5f15\u8303\u56f4\u626b\u63cf\u540e\u53d6\u5f97\u76ee\u6807 rowid \u518d\u56de\u8868\u53bb\u8bbf\u95ee\u5bf9\u5e94\u8868\u5757\u7684\u6570\u636e\u65f6\uff0c\u76f8\u90bb\u7684\u7d22\u5f15\u884c\u6240\u5bf9\u5e94\u7684 rowid \u6781\u6709\u53ef\u80fd\u5904\u4e8e\u540c\u4e00\u4e2a\u8868\u5757\uff0c\u4e5f\u5c31\u66f4\u5bb9\u6613\u547d\u4e2d\u7f13\u5b58\u3002<\/p>\n<p>\u56e0\u6b64\u5bf9\u4e8e\u7d22\u5f15\u8303\u56f4\u626b\u63cf\uff0c\u805a\u65cf\u56e0\u5b50\u9ad8\u7684\u6bd4\u4f4e\u7684\u9700\u8981\u8017\u8d39\u66f4\u591a\u7684\u7269\u7406 I\/O \uff0c\u6210\u672c\u66f4\u9ad8\u3002<\/p>\n<p>\u5728 Oracle \u6570\u636e\u5e93\u91cc\uff0c\u80fd\u591f\u964d\u4f4e\u76ee\u6807\u7d22\u5f15\u7684\u805a\u65cf\u56e0\u5b50\u7684\u552f\u4e00\u65b9\u6cd5\u5c31\u662f\u5bf9\u8868\u4e2d\u6570\u636e\u5757\u6309\u7167\u76ee\u6807\u7d22\u5f15\u7684\u7d22\u5f15\u952e\u503c\u6392\u5e8f\u540e\u91cd\u65b0\u5b58\u50a8\u3002\u4f46\u8fd9\u79cd\u65b9\u6cd5\u4e5f\u53ef\u80fd\u4f1a\u589e\u52a0\u8be5\u8868\u4e0a\u5176\u4ed6\u7d22\u5f15\u7684\u805a\u65cf\u56e0\u5b50\u7684\u503c\u3002<\/p>\n<p>\u805a\u65cf\u56e0\u5b50\u503c\u7684\u5927\u5c0f\u5b9e\u9645\u4e0a\u5bf9 CBO \u5224\u65ad\u662f\u5426\u8d70\u76f8\u5173\u7684\u7d22\u5f15\u8d77\u7740\u81f3\u5173\u91cd\u8981\u7684\u4f5c\u7528\u3002<\/p>\n<h3>\u8c13\u8bcd\u8d8a\u754c \u4e0e \u76f4\u65b9\u56fe<\/h3>\n<p>\u8c13\u8bcd\u8d8a\u754c\u662f\u6307\u5982\u679c\u5bf9\u76ee\u6807\u5217\u6307\u5b9a\u7684 where \u67e5\u8be2\u6761\u4ef6\u4e0d\u5728\u8be5\u5217\u7684\u6700\u5927\u503c\u4e0e\u6700\u5c0f\u503c\u4e4b\u95f4\uff0cCBO \u5c31\u65e0\u6cd5\u5224\u65ad\u51fa\u9488\u5bf9\u8be5\u5217\u7684\u67e5\u8be2\u6761\u4ef6\u7684\u53ef\u9009\u62e9\u7387\uff0c\u6240\u4ee5\u53ea\u80fd\u7528\u4e00\u4e2a\u4f30\u7b97\u503c\u6765\u4f5c\u4e3a\u9488\u5bf9\u8be5\u5217\u7684\u67e5\u8be2\u6761\u4ef6\u7684\u53ef\u9009\u62e9\u7387\uff0c\u5982\u679c\u8fd9\u4e2a\u4f30\u7b97\u7684\u53ef\u9009\u62e9\u7387\u4e0e\u5b9e\u9645\u60c5\u51b5\u4e25\u91cd\u4e0d\u7b26\uff0c\u786e\u5b9e\u53ef\u80fd\u5bfc\u81f4 CBO \u8bc4\u4f30\u51fa\u6765\u7684 Cardinality \u51fa\u73b0\u4e25\u91cd\u504f\u5dee\uff0c\u8fdb\u800c\u4f7f CBO \u9009\u9519\u6267\u884c\u8ba1\u5212\u3002<\/p>\n<p>CBO \u4f1a\u9ed8\u8ba4\u8ba4\u4e3a\u76ee\u6807\u5217\u7684\u6570\u636e\u5728\u5176\u6700\u5c0f\u503c LOW_VALUE \u548c\u6700\u5927\u503c HIGHT_VALUE \u4e4b\u95f4\u662f\u5747\u5300\u5206\u5e03\u7684\uff0c\u5e76\u4e14\u4f1a\u6309\u7167\u8fd9\u4e2a\u5747\u5300\u5206\u5e03\u539f\u5219\u6765\u8ba1\u7b97\u5bf9\u76ee\u6807\u5217\u65bd\u52a0\u67e5\u8be2\u6761\u4ef6\u540e\u7684\u53ef\u9009\u62e9\u7387\u4ee5\u53ca\u7ed3\u679c\u96c6\u7684 Cardinality\uff0c\u8fdb\u800c\u636e\u6b64\u6765\u8ba1\u7b97\u6210\u672c\u503c\u5e76\u9009\u62e9\u6267\u884c\u8ba1\u5212\u3002\u56e0\u6b64\uff0c\u5982\u679c\u503c\u662f\u4e0d\u5747\u5300\u5206\u5e03\u7684\uff0cCBO \u53ef\u80fd\u9009\u9519\u6267\u884c\u8ba1\u5212\u3002<\/p>\n<p>\u5982\u679c\u5bf9\u76ee\u6807\u5217\u6536\u96c6\u4e86\u76f4\u65b9\u56fe\uff08Histogram\uff09\uff0c\u5219\u610f\u5473\u7740 CBO \u4e0d\u518d\u8ba4\u4e3a\u8be5\u76ee\u6807\u5217\u4e0a\u7684\u6570\u636e\u662f\u5747\u5300\u5206\u5e03\u7684\uff0c CBO \u4f1a\u7528\u8be5\u76ee\u6807\u5217\u4e0a\u7684\u76f4\u65b9\u56fe\u7edf\u8ba1\u4fe1\u606f\u6765\u8ba1\u7b97\u5bf9\u8be5\u5217\u65bd\u52a0\u67e5\u8be2\u6761\u4ef6\u540e\u7684\u53ef\u9009\u62e9\u7387\u548c\u8fd4\u56de\u7ed3\u679c\u96c6\u7684 Cardinality\uff0c\u8fdb\u800c\u636e\u6b64\u8ba1\u7b97\u6210\u672c\u5e76\u9009\u62e9\u6267\u884c\u8ba1\u5212\u3002<\/p>\n<p>\u6848\u4f8b\uff1a\u5f88\u591a\u4e1a\u52a1\u6570\u636e\u5728\u5904\u7406\u5b8c\u540e\u4f1a\u628a\u72b6\u6001\u5b57\u6bb5 <code>status<\/code> \u4ece <code>0<\/code> \u6807\u8bb0\u4e3a <code>1<\/code>\uff0c\u65f6\u95f4\u8d8a\u957f\uff0c\u72b6\u6001\u4e3a 1 \u7684\u6570\u636e\u5c31\u5360\u5c45\u4e86\u7edd\u5927\u90e8\u5206\uff0c\u6bcf\u6b21\u67e5\u8be2\u90fd\u662f\u67e5\u72b6\u6001\u4e3a 0 \u7684\u6570\u636e\uff0c\u56e0\u6b64\u53ef\u4ee5\u5728\u72b6\u6001\u5b57\u6bb5\u4e0a\u5efa\u7acb\u7d22\u5f15\u3002\u67e5\u770b\u6267\u884c\u8ba1\u5212\u65f6\uff0cstatus \u5bf9\u5e94\u7684\u503c\u7528\u5360\u4f4d\u7b26\u6216 1 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