{"id":95582,"date":"2024-10-20T02:16:16","date_gmt":"2024-10-19T18:16:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/95582\/"},"modified":"2024-10-20T02:16:16","modified_gmt":"2024-10-19T18:16:16","slug":"oracle%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84dual%ef%bc%9a%e5%a4%9a%e5%8a%9f%e8%83%bd%e7%9a%84%e5%88%a9%e5%99%a8-oracle%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84dual","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/95582\/","title":{"rendered":"Oracle\u6578\u64da\u5eab\u7684DUAL\uff1a\u591a\u529f\u80fd\u7684\u5229\u5668 (oracle\u6578\u64da\u5eab\u7684dual)"},"content":{"rendered":"<h1 id=\"oracle%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84dual%ef%bc%9a%e5%a4%9a%e5%8a%9f%e8%83%bd%e7%9a%84%e5%88%a9%e5%99%a8-XnXNigeBqX\">Oracle\u6578\u64da\u5eab\u7684DUAL\uff1a\u591a\u529f\u80fd\u7684\u5229\u5668<\/h1>\n<p>\u5728Oracle\u6578\u64da\u5eab\u4e2d\uff0cDUAL\u662f\u4e00\u500b\u7279\u6b8a\u7684\u865b\u64ec\u8868\uff0c\u7d93\u5e38\u88ab\u7528\u4f86\u57f7\u884c\u67e5\u8a62\u548c\u8a08\u7b97\u3002\u9019\u500b\u8868\u7684\u5b58\u5728\u4f7f\u5f97\u7528\u6236\u80fd\u5920\u5728\u4e0d\u9700\u8981\u5be6\u969b\u6578\u64da\u8868\u7684\u60c5\u6cc1\u4e0b\u9032\u884c\u64cd\u4f5c\uff0c\u5f9e\u800c\u63d0\u9ad8\u4e86\u67e5\u8a62\u7684\u9748\u6d3b\u6027\u548c\u6548\u7387\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eDUAL\u7684\u529f\u80fd\u3001\u7528\u9014\u53ca\u5176\u5728\u65e5\u5e38\u6578\u64da\u5eab\u64cd\u4f5c\u4e2d\u7684\u91cd\u8981\u6027\u3002<\/p>\n<h2 id=\"dual%e8%a1%a8%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-XnXNigeBqX\">DUAL\u8868\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>DUAL\u8868\u662f\u4e00\u500b\u55ae\u884c\u55ae\u5217\u7684\u865b\u64ec\u8868\uff0cOracle\u6578\u64da\u5eab\u5728\u5b89\u88dd\u6642\u81ea\u52d5\u5275\u5efa\u3002\u9019\u500b\u8868\u7684\u4e3b\u8981\u76ee\u7684\u662f\u63d0\u4f9b\u4e00\u500b\u7c21\u55ae\u7684\u67e5\u8a62\u74b0\u5883\uff0c\u8b93\u7528\u6236\u80fd\u5920\u57f7\u884c\u4e0d\u4f9d\u8cf4\u65bc\u4efb\u4f55\u5be6\u969b\u6578\u64da\u8868\u7684SQL\u67e5\u8a62\u3002DUAL\u8868\u7684\u7d50\u69cb\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT dummy FROM DUAL;<\/code><\/pre>\n<p>\u57f7\u884c\u4e0a\u8ff0\u67e5\u8a62\u5c07\u8fd4\u56de\u4e00\u500b\u540d\u70ba\u201cX\u201d\u7684\u503c\uff0c\u9019\u662fDUAL\u8868\u4e2d\u552f\u4e00\u7684\u6578\u64da\u3002<\/p>\n<h2 id=\"dual%e7%9a%84%e4%b8%bb%e8%a6%81%e7%94%a8%e9%80%94-XnXNigeBqX\">DUAL\u7684\u4e3b\u8981\u7528\u9014<\/h2>\n<ul>\n<li><strong>\u8a08\u7b97\u548c\u51fd\u6578\u8abf\u7528\uff1a<\/strong>DUAL\u8868\u5e38\u7528\u65bc\u57f7\u884c\u6578\u5b78\u8a08\u7b97\u6216\u8abf\u7528Oracle\u5167\u5efa\u51fd\u6578\u3002\u4f8b\u5982\uff0c\u4f7f\u7528DUAL\u4f86\u8a08\u7b97\u7576\u524d\u65e5\u671f\uff1a<\/li>\n<\/ul>\n<pre><code>SELECT SYSDATE FROM DUAL;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u7576\u524d\u7684\u7cfb\u7d71\u65e5\u671f\u548c\u6642\u9593\u3002<\/p>\n<ul>\n<li><strong>\u751f\u6210\u5e8f\u5217\u865f\uff1a<\/strong>\u5728\u9700\u8981\u751f\u6210\u5e8f\u5217\u865f\u6216\u552f\u4e00\u6a19\u8b58\u7b26\u6642\uff0cDUAL\u8868\u4e5f\u975e\u5e38\u6709\u7528\u3002\u4f8b\u5982\uff1a<\/li>\n<\/ul>\n<pre><code>SELECT my_sequence.NEXTVAL FROM DUAL;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u5e8f\u5217\u7684\u4e0b\u4e00\u500b\u503c\u3002<\/p>\n<ul>\n<li><strong>\u6e2c\u8a66\u67e5\u8a62\uff1a<\/strong>\u958b\u767c\u4eba\u54e1\u5728\u6e2c\u8a66SQL\u67e5\u8a62\u6642\uff0cDUAL\u8868\u63d0\u4f9b\u4e86\u4e00\u500b\u7c21\u55ae\u7684\u74b0\u5883\u4f86\u9a57\u8b49\u67e5\u8a62\u7684\u6b63\u78ba\u6027\uff0c\u800c\u4e0d\u9700\u8981\u4f9d\u8cf4\u65bc\u5be6\u969b\u7684\u6578\u64da\u8868\u3002<\/li>\n<\/ul>\n<pre><code>SELECT 'Hello, World!' FROM DUAL;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u4e00\u500b\u5b57\u7b26\u4e32\uff0c\u65b9\u4fbf\u958b\u767c\u4eba\u54e1\u9032\u884c\u6e2c\u8a66\u3002<\/p>\n<h2 id=\"dual%e7%9a%84%e6%80%a7%e8%83%bd%e8%80%83%e9%87%8f-XnXNigeBqX\">DUAL\u7684\u6027\u80fd\u8003\u91cf<\/h2>\n<p>\u7531\u65bcDUAL\u662f\u4e00\u500b\u865b\u64ec\u8868\uff0c\u67e5\u8a62DUAL\u7684\u6027\u80fd\u901a\u5e38\u975e\u5e38\u9ad8\u6548\u3002\u5b83\u4e0d\u9700\u8981\u9032\u884c\u78c1\u789fI\/O\u64cd\u4f5c\uff0c\u56e0\u70ba\u6240\u6709\u7684\u6578\u64da\u90fd\u5728\u5167\u5b58\u4e2d\u8655\u7406\u3002\u56e0\u6b64\uff0c\u5728\u9700\u8981\u983b\u7e41\u57f7\u884c\u7c21\u55ae\u67e5\u8a62\u7684\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528DUAL\u8868\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n<h2 id=\"dual%e7%9a%84%e9%99%90%e5%88%b6-XnXNigeBqX\">DUAL\u7684\u9650\u5236<\/h2>\n<p>\u5118\u7ba1DUAL\u8868\u529f\u80fd\u5f37\u5927\uff0c\u4f46\u5b83\u4e5f\u6709\u4e00\u4e9b\u9650\u5236\u3002\u9996\u5148\uff0cDUAL\u8868\u53ea\u80fd\u8fd4\u56de\u4e00\u884c\u6578\u64da\uff0c\u9019\u610f\u5473\u8457\u5982\u679c\u9700\u8981\u8fd4\u56de\u591a\u884c\u6578\u64da\uff0c\u5247\u5fc5\u9808\u4f7f\u7528\u5176\u4ed6\u5be6\u969b\u7684\u6578\u64da\u8868\u3002\u6b64\u5916\uff0cDUAL\u8868\u4e0d\u652f\u6301\u63d2\u5165\u3001\u66f4\u65b0\u6216\u522a\u9664\u64cd\u4f5c\uff0c\u56e0\u70ba\u5b83\u4e0d\u662f\u771f\u6b63\u7684\u6578\u64da\u8868\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-XnXNigeBqX\">\u7d50\u8ad6<\/h2>\n<p>\u7e3d\u7684\u4f86\u8aaa\uff0cOracle\u6578\u64da\u5eab\u4e2d\u7684DUAL\u8868\u662f\u4e00\u500b\u591a\u529f\u80fd\u7684\u5229\u5668\uff0c\u70ba\u7528\u6236\u63d0\u4f9b\u4e86\u9748\u6d3b\u7684\u67e5\u8a62\u9078\u64c7\u3002\u7121\u8ad6\u662f\u9032\u884c\u7c21\u55ae\u7684\u8a08\u7b97\u3001\u751f\u6210\u5e8f\u5217\u865f\uff0c\u9084\u662f\u6e2c\u8a66SQL\u67e5\u8a62\uff0cDUAL\u8868\u90fd\u80fd\u5920\u9ad8\u6548\u5730\u6eff\u8db3\u9700\u6c42\u3002\u4e86\u89e3DUAL\u7684\u4f7f\u7528\u65b9\u6cd5\u548c\u7279\u6027\uff0c\u5c0d\u65bc\u6578\u64da\u5eab\u958b\u767c\u4eba\u54e1\u548c\u7ba1\u7406\u54e1\u4f86\u8aaa\uff0c\u90fd\u662f\u4e00\u9805\u91cd\u8981\u7684\u6280\u80fd\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u60a8\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u670d\u52d9\uff0c\u6211\u5011\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22Oracle\u6578\u64da\u5eab\u4e2d\u7684DUAL\u8868\uff0c\u4e86\u89e3\u5176\u591a\u529f\u80fd\u6027\u53ca\u5728\u67e5\u8a62\u3001\u8a08\u7b97\u548c\u6578\u64da\u8655\u7406\u4e2d\u7684\u91cd\u8981\u89d2\u8272\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-95582","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95582","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=95582"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95582\/revisions"}],"predecessor-version":[{"id":95583,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95582\/revisions\/95583"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=95582"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=95582"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=95582"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}