\u89c6\u56fe\u7279\u70b9\uff1a
\n1,\u89c6\u56fe\u7684\u5217\u53ef\u4ee5\u6765\u81ea\u4e0d\u540c\u7684\u8868\uff0c\u662f\u8868\u7684\u62bd\u8c61\u548c\u5728\u903b\u8f91\u610f\u4e49\u4e0a\u5efa\u7acb\u7684\u65b0\u5173\u7cfb\u3002
\n2,\u89c6\u56fe\u662f\u7531\u57fa\u672c\u8868\uff08\u5b9e\u8868\uff09\u4ea7\u751f\u7684\u8868\uff08\u865a\u8868\uff09\u3002
\n3,\u89c6\u56fe\u7684\u5efa\u7acb\u548c\u5220\u9664\u4e0d\u5f71\u54cd\u57fa\u672c\u8868\u3002
\n4,\u5bf9\u89c6\u56fe\u5185\u5bb9\u7684\u66f4\u65b0\uff08\u6dfb\u52a0\uff0c\u5220\u9664\u548c\u4fee\u6539\uff09\u76f4\u63a5\u5f71\u54cd\u57fa\u672c\u8868\u3002
\n5,\u5f53\u89c6\u56fe\u6765\u81ea\u591a\u4e2a\u57fa\u672c\u8868\u65f6\uff0c\u4e0d\u5141\u8bb8\u6dfb\u52a0\u548c\u5220\u9664\u6570\u636e\u3002
\n\u89c6\u56fe\u7528\u9014\uff1a\u7b80\u5316sql\u67e5\u8be2\uff0c\u63d0\u9ad8\u5f00\u53d1\u6548\u7387\uff0c\u517c\u5bb9\u8001\u7684\u8868\u7ed3\u6784\u3002
\n\u89c6\u56fe\u7684\u5e38\u89c1\u4f7f\u7528\u573a\u666f\uff1a
\n1\u3001\t\u91cd\u7528SQL\u8bed\u53e5\uff1b
\n2\u3001\t\u7b80\u5316\u590d\u6742\u7684SQL\u64cd\u4f5c\u3002
\n3\u3001\t\u4f7f\u7528\u8868\u7684\u7ec4\u6210\u90e8\u5206\u800c\u4e0d\u662f\u6574\u4e2a\u8868\uff1b
\n4\u3001\t\u4fdd\u62a4\u6570\u636e
\n5\u3001\t\u66f4\u6539\u6570\u636e\u683c\u5f0f\u548c\u8868\u793a\u3002\u89c6\u56fe\u53ef\u8fd4\u56de\u4e0e\u5e95\u5c42\u8868\u7684\u8868\u793a\u548c\u683c\u5f0f\u4e0d\u540c\u7684\u6570\u636e\u3002
\nMySQL\u4e2din\u548cexists\u7684\u533a\u522b\u3002
\n\u8fd9\u4e2a\uff0c\u8ddf\u4e00\u4e0bdemo\u6765\u770b\u66f4\u523a\u6fc0\u5427\uff0c\u554a\u54c8\u54c8
\n\u5047\u8bbe\u8868A\u8868\u793a\u67d0\u4f01\u4e1a\u7684\u5458\u5de5\u8868\uff0c\u8868B\u8868\u793a\u90e8\u95e8\u8868\uff0c\u67e5\u8be2\u6240\u6709\u90e8\u95e8\u7684\u6240\u6709\u5458\u5de5\uff0c\u5f88\u5bb9\u6613\u6709\u4ee5\u4e0bSQL\uff1a
\nselect * from A where deptId in \uff08select deptId from B\uff09\uff1b
\n\u8fd9\u6837\u5199\u7b49\u4ef7\u4e8e\uff1a
\n1\u3001\t\u5148\u67e5\u8be2\u90e8\u95e8\u8868B
\n2\u3001\tselect deptld from B
\n3\u3001\t\u518d\u7531\u90e8\u95e8deptId,\u67e5\u8be2A\u7684\u5458\u5de5
\n4\u3001\tselect * from A where A. deptId = B.deptId
\n\u53ef\u4ee5\u62bd\u8c61\u6210\u8fd9\u6837\u7684\u4e00\u4e2a\u5faa\u73af\uff1a
\nList<> resultSet \uff1b
\nfor(int i=0\uff1bi<B.length\uff1bi++) {
\nfor(int j=0\uff1bj<A.length\uff1bj++) {
\nif (A[i].id=B[j].id) {
\nresultSet.add(A[i])\uff1b
\nbreak\uff1b
\n}
\n}
\n}
\n\u663e\u7136\uff0c\u9664\u4e86\u4f7f\u7528in,\u6211\u4eec\u4e5f\u53ef\u4ee5\u7528exists\u5b9e\u73b0\u4e00\u6837\u7684\u67e5\u8be2\u529f\u80fd\uff0c\u5982\u4e0b:
\nselect * from A where exists (select 1 from B where A.deptId = B.deptId)\uff1b
\n\u56e0\u4e3aexists\u67e5\u8be2\u7684\u7406\u89e3\u5c31\u662f\uff0c\u5148\u6267\u884c\u4e3b\u67e5\u8be2\uff0c\u83b7\u5f97\u6570\u636e\u540e\uff0c\u518d\u653e\u5230\u5b50\u67e5\u8be2\u4e2d\u505a\u6761\u4ef6\u9a8c\u8bc1\uff0c\u6839\u636e\u9a8c\u8bc1\u7ed3\u679c\uff08true\u6216\u8005false\uff09,\u6765\u51b3\u5b9a\u4e3b\u67e5\u8be2\u7684\u6570\u636e\u7ed3\u679c\u662f\u5426\u5f97\u610f\u4fdd\u7559\u3002
\n\u90a3\u4e48\uff0c\u8fd9\u6837\u5199\u5c31\u7b49\u4ef7\u4e8e\uff1a
\nselect * from A,\u5148\u4eceA\u8868\u505a\u5faa\u73af
\nselect * from B where A.deptld = B.deptld,\u518d\u4ece B \u8868\u505a\u5faa\u73af.
\n\u540c\u7406\uff0c\u53ef\u4ee5\u62bd\u8c61\u6210\u8fd9\u6837\u4e00\u4e2a\u5faa\u73af\uff1a
\nList<> resultSet \uff1b
\nfor(int i=0\uff1bi<A.length\uff1bi++) {
\nfor(int j=0\uff1bj<B.length\uff1bj++) {
\nif (A[i].deptId=B[j].deptId) {
\nresultSet.add(A[i])\uff1b
\nbreak\uff1b
\n}
\n}
\n}
\n\u6570\u636e\u5e93\u6700\u8d39\u52b2\u7684\u5c31\u662f\u8ddf\u7a0b\u5e8f\u94fe\u63a5\u91ca\u653e\u3002\u5047\u8bbe\u94fe\u63a5\u4e86\u4e24\u6b21\uff0c\u6bcf\u6b21\u505a\u4e0a\u767e\u4e07\u6b21\u7684\u6570\u636e\u96c6\u67e5\u8be2\uff0c\u67e5\u5b8c\u5c31\u8d70\uff0c\u8fd9\u6837\u5c31\u53ea\u505a\u4e86\u4e24\u6b21\uff1b\u76f8\u53cd\u5efa\u7acb\u4e86\u4e0a\u767e\u4e07\u6b21\u94fe\u63a5\uff0c\u7533\u8bf7\u94fe\u63a5\u91ca\u653e\u53cd\u590d\u91cd\u590d\uff0c\u8fd9\u6837\u7cfb\u7edf\u5c31\u53d7\u4e0d\u4e86\u4e86\u3002\u5373MySQL\u4f18\u5316\u539f\u5219\uff0c\u5c31\u662f\u5c0f\u8868\u9a71\u52a8\u5927\u8868\uff0c\u5c0f\u7684\u6570\u636e\u96c6\u9a71\u52a8\u5927\u7684\u6570\u636e\u96c6\uff0c\u4ece\u800c\u8ba9\u6027\u80fd\u66f4\u4f18\u3002
\n\u56e0\u6b64\uff0c\u6211\u4eec\u8981\u9009\u62e9\u6700\u5916\u5c42\u5faa\u73af\u5c0f\u7684\uff0c\u4e5f\u5c31\u662f\uff0c\u5982\u679cB\u7684\u6570\u636e\u91cf\u5c0f\u4e8eA,\u9002\u5408\u4f7f\u7528in,\u5982\u679cB \u7684\u6570\u636e\u91cf\u5927\u4e8eA,\u5373\u9002\u5408\u9009\u62e9exists,\u8fd9\u5c31\u662fin\u548cexists\u7684\u533a\u522b\u3002
\nMySQL \u4e2d drop\u3001delete \u4e0e truncate \u7684\u533a\u522b\uff1f
\n1\u3001\tDELETE\u8bed\u53e5\u6267\u884c\u5220\u9664\u7684\u8fc7\u7a0b\u662f\u6bcf\u6b21\u4ece\u8868\u4e2d\u5220\u9664\u4e00\u884c\uff0c\u5e76\u4e14\u540c\u65f6\u5c06\u8be5\u884c\u7684\u5220\u9664\u64cd\u4f5c\u4f5c\u4e3a\u4e8b\u52a1\u8bb0\u5f55\u5728\u65e5\u5fd7\u4e2d\u4fdd\u5b58\u4ee5\u4fbf\u8fdb\u884c\u56de\u6eda\u64cd\u4f5c\u3002TRUNCATE TABLE\u5219\u4e00\u6b21\u6027\u5730\u4ece\u8868\u4e2d\u5220\u9664\u6240\u6709\u7684\u6570\u636e\u5e76\u4e0d\u628a\u5355\u72ec\u7684\u5220\u9664\u64cd\u4f5c\u8bb0\u5f55\u8bb0\u5165\u65e5\u5fd7\u4fdd\u5b58\uff0c\u5220\u9664\u884c\u662f\u4e0d\u80fd\u6062\u590d\u7684\u3002\u5e76\u4e14\u5728\u5220\u9664\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u4f1a\u6fc0\u6d3b\u4e0e\u8868\u6709\u5173\u7684\u5220\u9664\u89e6\u53d1\u5668\u3002\u6267\u884c\u901f\u5ea6\u5feb\u3002
\n2\u3001\t\u8868\u548c\u7d22\u5f15\u6240\u5360\u7a7a\u95f4\u3002\u5f53\u8868\u88abTRUNCATE\u540e\uff0c\u8fd9\u4e2a\u8868\u548c\u7d22\u5f15\u6240\u5360\u7528\u7684\u7a7a\u95f4\u4f1a\u6062\u590d\u5230\u521d\u59cb\u5927\u5c0f, \u800cDELETE\u64cd\u4f5c\u4e0d\u4f1a\u51cf\u5c11\u8868\u6216\u7d22\u5f15\u6240\u5360\u7528\u7684\u7a7a\u95f4\u3002drop\u8bed\u53e5\u5c06\u8868\u6240\u5360\u7528\u7684\u7a7a\u95f4\u5168\u91ca\u653e\u6389\u3002
\n3\u3001\t\u4e00\u822c\u800c\u8a00\uff0cdrop > truncate > delete
\n4\u3001\t\u5e94\u7528\u8303\u56f4\u3002TRUNCATE\u53ea\u80fd\u5bf9TABLE\uff1b DELETE\u53ef\u4ee5\u662ftable\u548cview
\n5\u3001\tTRUNCATE\u548cDELETE\u53ea\u5220\u9664\u6570\u636e\uff0c\u800cDROP\u5219\u5220\u9664\u6574\u4e2a\u8868(\u7ed3\u6784\u548c\u6570\u636e)\u3002
\n6\u3001\ttruncate\u4e0e\u4e0d\u5e26where\u7684delete \uff1a\u53ea\u5220\u9664\u6570\u636e\uff0c\u800c\u4e0d\u5220\u9664\u8868\u7684\u7ed3\u6784(\u5b9a\u4e49)drop\u8bed\u53e5\u5c06\u5220\u9664\u8868\u7684\u7ed3\u6784\u88ab\u4f9d\u8d56\u7684\u7ea6\u675f(constrain),\u89e6\u53d1\u5668(trigger)\u7d22\u5f15(index)\uff1b\u4f9d\u8d56\u4e8e\u8be5\u8868\u7684\u5b58\u50a8\u8fc7\u7a0b\/\u51fd\u6570\u5c06\u88ab\u4fdd\u7559\uff0c\u4f46\u5176\u72b6\u6001\u4f1a\u53d8\u4e3a\uff1ainvalid\u3002
\n7\u3001\tdelete \u8bed\u53e5\u4e3a DML (data maintain Language),\u8fd9\u4e2a\u64cd\u4f5c\u4f1a\u88ab\u653e\u5230 rollback segment \u4e2d\uff0c\u4e8b\u52a1\u63d0\u4ea4\u540e\u624d\u751f\u6548\u3002\u5982\u679c\u6709\u76f8\u5e94\u7684trigger,\u6267\u884c\u7684\u65f6\u5019\u5c06\u88ab\u89e6\u53d1\u3002
\n8\u3001\ttruncate, drop \u662f DLL \uff08data define language\uff09,\u64cd\u4f5c\u7acb\u5373\u751f\u6548\uff0c\u539f\u6570\u636e\u4e0d\u653e\u5230rollback segment\u4e2d\uff0c\u4e0d\u80fd\u56de\u6eda
\n9\u3001\t\u5728\u6ca1\u6709\u5907\u4efd\u60c5\u51b5\u4e0b\uff0c\u8c28\u614e\u4f7f\u7528drop\u4e0etruncate\u3002\u8981\u5220\u9664\u90e8\u5206\u6570\u636e\u884c\u91c7\u7528delete\u4e14\u6ce8\u610f\u7ed3\u5408where\u6765\u7ea6\u675f\u5f71\u54cd\u8303\u56f4\u3002\u56de\u6eda\u6bb5\u8981\u8db3\u591f\u5927\u3002\u8981\u5220\u9664\u8868\u7528drop\uff1b\u82e5\u60f3\u4fdd\u7559\u8868\u800c\u5c06\u8868\u4e2d\u6570\u636e\u5220\u9664\uff0c\u5982\u679c\u4e8e\u4e8b\u52a1\u65e0\u5173\uff0c\u7528truncate\u5373\u53ef\u5b9e\u73b0\u3002\u5982\u679c\u548c\u4e8b\u52a1\u6709\u5173\uff0c\u6216\u60f3\u89e6\u53d1trigger,\u8fd8\u662f\u7528delete\u3002
\n10\u3001\tTruncate table\u8868\u540d\u901f\u5ea6\u5feb\uff0c\u800c\u4e14\u6548\u7387\u9ad8\uff0c\u56e0\u4e3a:truncate table\u5728\u529f\u80fd\u4e0a\u4e0e\u4e0d\u5e26 WHERE\u5b50\u53e5\u7684DELETE\u8bed\u53e5\u76f8\u540c\uff1a\u4e8c\u8005\u5747\u5220\u9664\u8868\u4e2d\u7684\u5168\u90e8\u884c\u3002\u4f46TRUNCATE TABLE\u6bd4DELETE \u901f\u5ea6\u5feb\uff0c\u4e14\u4f7f\u7528\u7684\u7cfb\u7edf\u548c\u4e8b\u52a1\u65e5\u5fd7\u8d44\u6e90\u5c11\u3002DELETE\u8bed\u53e5\u6bcf\u6b21\u5220\u9664\u4e00\u884c\uff0c\u5e76\u5728\u4e8b\u52a1\u65e5\u5fd7\u4e2d\u4e3a\u6240\u5220\u9664\u7684\u6bcf\u884c\u8bb0\u5f55\u4e00\u9879\u3002TRUNCATE TABLE\u901a\u8fc7\u91ca\u653e\u5b58\u50a8\u8868\u6570\u636e\u6240\u7528\u7684\u6570\u636e\u9875\u6765\u5220\u9664\u6570\u636e\uff0c\u5e76\u4e14\u53ea\u5728\u4e8b\u52a1\u65e5\u5fd7\u4e2d\u8bb0\u5f55\u9875\u7684\u91ca\u653e\u3002
\n11\u3001\tTRUNCATE TABLE\u5220\u9664\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u4f46\u8868\u7ed3\u6784\u53ca\u5176\u5217\u3001\u7ea6\u675f\u3001\u7d22\u5f15\u7b49\u4fdd\u6301\u4e0d\u53d8\u3002\u65b0\u884c\u6807\u8bc6\u6240\u7528\u7684\u8ba1\u6570\u503c\u91cd\u7f6e\u4e3a\u8be5\u5217\u7684\u79cd\u5b50\u3002\u5982\u679c\u60f3\u4fdd\u7559\u6807\u8bc6\u8ba1\u6570\u503c\uff0c\u8bf7\u6539\u7528DELETE\u3002\u5982\u679c\u8981\u5220\u9664\u8868\u5b9a\u4e49\u53ca\u5176\u6570\u636e\uff0c\u8bf7\u4f7f\u7528DROP TABLE\u8bed\u53e5\u3002
\n12\u3001\t\u5bf9\u4e8e\u7531FOREIGN KEY\u7ea6\u675f\u5f15\u7528\u7684\u8868\uff0c\u4e0d\u80fd\u4f7f\u7528TRUNCATE TABLE,\u800c\u5e94\u4f7f\u7528\u4e0d\u5e26WHERE \u5b50\u53e5\u7684DELETE\u8bed\u53e5\u3002\u7531\u4e8eTRUNCATE TABLE\u4e0d\u8bb0\u5f55\u5728\u65e5\u5fd7\u4e2d\uff0c\u6240\u4ee5\u5b83\u4e0d\u80fd\u6fc0\u6d3b\u89e6\u53d1\u5668\u3002
\nMySQL\u4e2dMyISAM\u7d22\u5f15\u4e0eInnoDB\u7d22\u5f15\u7684\u533a\u522b\uff1f
\n1\u3001\tInnoDB\u7d22\u5f15\u662f\u805a\u7c07\u7d22\u5f15\uff0cMyISAM\u7d22\u5f15\u662f\u975e\u805a\u7c07\u7d22\u5f15\u3002
\n2\u3001\tInnoDB\u7684\u4e3b\u952e\u7d22\u5f15\u7684\u53f6\u5b50\u8282\u70b9\u5b58\u50a8\u7740\u884c\u6570\u636e\uff0c\u56e0\u6b64\u4e3b\u952e\u7d22\u5f15\u975e\u5e38\u9ad8\u6548\u3002
\n3\u3001\tMyISAM\u7d22\u5f15\u7684\u53f6\u5b50\u8282\u70b9\u5b58\u50a8\u7684\u662f\u884c\u6570\u636e\u5730\u5740\uff0c\u9700\u8981\u518d\u5bfb\u5740\u4e00\u6b21\u624d\u80fd\u5f97\u5230\u6570\u636e\u3002
\n4\u3001\tInnoDB\u975e\u4e3b\u952e\u7d22\u5f15\u7684\u53f6\u5b50\u8282\u70b9\u5b58\u50a8\u7684\u662f\u4e3b\u952e\u548c\u5176\u4ed6\u5e26\u7d22\u5f15\u7684\u5217\u6570\u636e\uff0c\u56e0\u6b64\u67e5\u8be2\u65f6\u505a\u5230\u8986\u76d6\u7d22\u5f15\u4f1a\u975e\u5e38\u9ad8\u6548\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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