{"id":95950,"date":"2024-10-20T05:21:15","date_gmt":"2024-10-19T21:21:15","guid":{"rendered":"https:\/\/server.hk\/cnblog\/95950\/"},"modified":"2024-10-20T05:21:16","modified_gmt":"2024-10-19T21:21:16","slug":"oracle%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%adnull%e7%9a%84%e5%85%b7%e9%ab%94%e4%bd%bf%e7%94%a8%e6%96%b9%e6%a1%88","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/95950\/","title":{"rendered":"Oracle\u6578\u64da\u5eab\u4e2dNULL\u7684\u5177\u9ad4\u4f7f\u7528\u65b9\u6848"},"content":{"rendered":"<h1 id=\"oracle%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%adnull%e7%9a%84%e5%85%b7%e9%ab%94%e4%bd%bf%e7%94%a8%e6%96%b9%e6%a1%88-PaubkcLQFi\">Oracle\u6578\u64da\u5eab\u4e2dNULL\u7684\u5177\u9ad4\u4f7f\u7528\u65b9\u6848<\/h1>\n<p>\u5728Oracle\u6578\u64da\u5eab\u4e2d\uff0cNULL\u662f\u4e00\u500b\u7279\u6b8a\u7684\u6a19\u8a18\uff0c\u7528\u65bc\u8868\u793a\u7f3a\u5931\u6216\u672a\u77e5\u7684\u6578\u64da\u3002\u7406\u89e3NULL\u7684\u4f7f\u7528\u5c0d\u65bc\u6578\u64da\u5eab\u8a2d\u8a08\u548c\u67e5\u8a62\u512a\u5316\u81f3\u95dc\u91cd\u8981\u3002\u672c\u6587\u5c07\u63a2\u8a0eNULL\u7684\u5b9a\u7fa9\u3001\u4f7f\u7528\u5834\u666f\u3001\u67e5\u8a62\u4e2d\u7684\u8655\u7406\u65b9\u5f0f\u4ee5\u53ca\u6700\u4f73\u5be6\u8e10\u3002<\/p>\n<h2 id=\"null%e7%9a%84%e5%ae%9a%e7%be%a9-PaubkcLQFi\">NULL\u7684\u5b9a\u7fa9<\/h2>\n<p>\u5728Oracle\u4e2d\uff0cNULL\u4e26\u4e0d\u7b49\u540c\u65bc\u96f6\u6216\u7a7a\u5b57\u7b26\u4e32\u3002\u5b83\u8868\u793a\u4e00\u500b\u503c\u7684\u7f3a\u5931\uff0c\u9019\u610f\u5473\u8457\u8a72\u5b57\u6bb5\u7684\u6578\u64da\u5c1a\u672a\u88ab\u5b9a\u7fa9\u3002\u9019\u4e00\u9ede\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\u975e\u5e38\u91cd\u8981\uff0c\u56e0\u70baNULL\u53ef\u4ee5\u5f71\u97ff\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u67e5\u8a62\u7684\u7d50\u679c\u3002<\/p>\n<h2 id=\"null%e7%9a%84%e4%bd%bf%e7%94%a8%e5%a0%b4%e6%99%af-PaubkcLQFi\">NULL\u7684\u4f7f\u7528\u5834\u666f<\/h2>\n<ul>\n<li><strong>\u53ef\u9078\u5b57\u6bb5\uff1a<\/strong>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6578\u64da\u5eab\u4e2d\u7684\u67d0\u4e9b\u5b57\u6bb5\u53ef\u80fd\u4e0d\u662f\u5fc5\u9700\u7684\u3002\u4f8b\u5982\uff0c\u5ba2\u6236\u7684\u4e2d\u9593\u540d\u53ef\u4ee5\u8a2d\u7f6e\u70baNULL\uff0c\u56e0\u70ba\u4e26\u975e\u6240\u6709\u5ba2\u6236\u90fd\u6709\u4e2d\u9593\u540d\u3002<\/li>\n<li><strong>\u7f3a\u5931\u6578\u64da\uff1a<\/strong>\u5728\u6578\u64da\u6536\u96c6\u904e\u7a0b\u4e2d\uff0c\u67d0\u4e9b\u4fe1\u606f\u53ef\u80fd\u7121\u6cd5\u7372\u5f97\uff0c\u9019\u6642\u53ef\u4ee5\u4f7f\u7528NULL\u4f86\u8868\u793a\u9019\u4e9b\u7f3a\u5931\u7684\u6578\u64da\u3002<\/li>\n<li><strong>\u72c0\u614b\u6a19\u8a18\uff1a<\/strong>\u5728\u67d0\u4e9b\u696d\u52d9\u908f\u8f2f\u4e2d\uff0cNULL\u53ef\u4ee5\u7528\u4f86\u8868\u793a\u67d0\u500b\u72c0\u614b\u5c1a\u672a\u88ab\u8a2d\u7f6e\u6216\u8655\u65bc\u672a\u5b9a\u7fa9\u7684\u72c0\u614b\u3002<\/li>\n<\/ul>\n<h2 id=\"%e6%9f%a5%e8%a9%a2%e4%b8%ad%e7%9a%84null%e8%99%95%e7%90%86-PaubkcLQFi\">\u67e5\u8a62\u4e2d\u7684NULL\u8655\u7406<\/h2>\n<p>\u5728SQL\u67e5\u8a62\u4e2d\uff0c\u8655\u7406NULL\u503c\u9700\u8981\u7279\u5225\u6ce8\u610f\u3002\u4f7f\u7528\u6a19\u6e96\u7684\u6bd4\u8f03\u904b\u7b97\u7b26\uff08\u5982=\u6216\uff09\u5c07\u7121\u6cd5\u6b63\u78ba\u8655\u7406NULL\u3002\u76f8\u53cd\uff0cOracle\u63d0\u4f9b\u4e86\u5c08\u9580\u7684\u904b\u7b97\u7b26\u4f86\u8655\u7406NULL\u503c\uff1a<\/p>\n<ul>\n<li><code>IS NULL<\/code>\uff1a\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u5b57\u6bb5\u662f\u5426\u70baNULL\u3002<\/li>\n<li><code>IS NOT NULL<\/code>\uff1a\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u5b57\u6bb5\u662f\u5426\u4e0d\u70baNULL\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\u67e5\u8a62\uff0c\u5c55\u793a\u5982\u4f55\u4f7f\u7528\u9019\u4e9b\u904b\u7b97\u7b26\uff1a<\/p>\n<pre><code>SELECT * FROM customers WHERE middle_name IS NULL;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u4e2d\u9593\u540d\u70baNULL\u7684\u5ba2\u6236\u8a18\u9304\u3002<\/p>\n<h2 id=\"null%e7%9a%84%e6%9c%80%e4%bd%b3%e5%af%a6%e8%b8%90-PaubkcLQFi\">NULL\u7684\u6700\u4f73\u5be6\u8e10<\/h2>\n<p>\u5728\u4f7f\u7528NULL\u6642\uff0c\u9075\u5faa\u4e00\u4e9b\u6700\u4f73\u5be6\u8e10\u53ef\u4ee5\u5e6b\u52a9\u63d0\u9ad8\u6578\u64da\u5eab\u7684\u6027\u80fd\u548c\u53ef\u7dad\u8b77\u6027\uff1a<\/p>\n<ul>\n<li><strong>\u660e\u78ba\u8a2d\u8a08\uff1a<\/strong>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u6642\uff0c\u61c9\u660e\u78ba\u54ea\u4e9b\u5b57\u6bb5\u53ef\u4ee5\u70baNULL\uff0c\u54ea\u4e9b\u5b57\u6bb5\u5fc5\u9808\u6709\u503c\u3002\u9019\u6709\u52a9\u65bc\u4fdd\u6301\u6578\u64da\u7684\u4e00\u81f4\u6027\u3002<\/li>\n<li><strong>\u4f7f\u7528\u9ed8\u8a8d\u503c\uff1a<\/strong>\u5c0d\u65bc\u67d0\u4e9b\u5b57\u6bb5\uff0c\u53ef\u4ee5\u8003\u616e\u4f7f\u7528\u9ed8\u8a8d\u503c\u4f86\u66ff\u4ee3NULL\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u67e5\u8a62\u6642\u7684\u8907\u96dc\u6027\u3002<\/li>\n<li><strong>\u5b9a\u671f\u6aa2\u67e5\uff1a<\/strong>\u5b9a\u671f\u6aa2\u67e5\u6578\u64da\u5eab\u4e2d\u7684NULL\u503c\uff0c\u78ba\u4fdd\u5b83\u5011\u7684\u5b58\u5728\u662f\u5408\u7406\u7684\uff0c\u4e26\u4e14\u4e0d\u6703\u5f71\u97ff\u696d\u52d9\u908f\u8f2f\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e8%ab%96-PaubkcLQFi\">\u7d50\u8ad6<\/h2>\n<p>NULL\u5728Oracle\u6578\u64da\u5eab\u4e2d\u662f\u4e00\u500b\u91cd\u8981\u7684\u6982\u5ff5\uff0c\u6b63\u78ba\u7406\u89e3\u548c\u4f7f\u7528NULL\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u597d\u5730\u8a2d\u8a08\u6578\u64da\u5eab\u548c\u64b0\u5beb\u67e5\u8a62\u3002\u901a\u904e\u9075\u5faa\u6700\u4f73\u5be6\u8e10\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u67e5\u8a62\u7684\u6548\u7387\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6216\u5176\u4ed6\u6280\u8853\u554f\u984c\u6709\u8208\u8da3\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4e86\u89e3\u66f4\u591a\u8cc7\u8a0a\uff0c\u7279\u5225\u662f\u6211\u5011\u7684<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u89e3\u6c7a\u65b9\u6848\uff0c\u9019\u5c07\u6709\u52a9\u65bc\u60a8\u66f4\u597d\u5730\u7ba1\u7406\u548c\u904b\u884c\u60a8\u7684\u61c9\u7528\u7a0b\u5e8f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22Oracle\u6578\u64da\u5eab\u4e2dNULL\u7684\u5177\u9ad4\u4f7f\u7528\u65b9\u6848\uff0c\u4e86\u89e3\u5982\u4f55\u8655\u7406\u7a7a\u503c\u4ee5\u512a\u5316\u6578\u64da\u67e5\u8a62\u548c\u7ba1\u7406\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-95950","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95950","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=95950"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95950\/revisions"}],"predecessor-version":[{"id":95951,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95950\/revisions\/95951"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=95950"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=95950"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=95950"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}