{"id":153963,"date":"2024-11-02T11:49:19","date_gmt":"2024-11-02T03:49:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/153963\/"},"modified":"2024-11-02T11:49:20","modified_gmt":"2024-11-02T03:49:20","slug":"%e7%9a%84%e8%99%95%e7%90%86%e6%96%b9%e6%b3%95%e6%95%b8%e6%93%9a%e5%ba%ab%e6%8e%92%e5%ba%8f%e4%b8%ad%e6%87%89%e5%a6%82%e4%bd%95%e8%99%95%e7%90%86null%e5%80%bc-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%8e%92","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/153963\/","title":{"rendered":"\u7684\u8655\u7406\u65b9\u6cd5\u6578\u64da\u5eab\u6392\u5e8f\u4e2d\u61c9\u5982\u4f55\u8655\u7406null\u503c (\u6578\u64da\u5eab\u6392\u5e8f\u6642null\u503c)"},"content":{"rendered":"<h1 id=\"%e7%9a%84%e8%99%95%e7%90%86%e6%96%b9%e6%b3%95%e6%95%b8%e6%93%9a%e5%ba%ab%e6%8e%92%e5%ba%8f%e4%b8%ad%e6%87%89%e5%a6%82%e4%bd%95%e8%99%95%e7%90%86null%e5%80%bc-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%8e%92-sFhgCTAuoW\">\u7684\u8655\u7406\u65b9\u6cd5\u6578\u64da\u5eab\u6392\u5e8f\u4e2d\u61c9\u5982\u4f55\u8655\u7406null\u503c (\u6578\u64da\u5eab\u6392\u5e8f\u6642null\u503c)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0c\u6392\u5e8f\u662f\u4e00\u500b\u5e38\u898b\u7684\u64cd\u4f5c\uff0c\u901a\u5e38\u7528\u65bc\u67e5\u8a62\u7d50\u679c\u7684\u986f\u793a\u3002\u7136\u800c\uff0c\u7576\u6578\u64da\u4e2d\u5305\u542b <code>NULL<\/code> \u503c\u6642\uff0c\u6392\u5e8f\u7684\u884c\u70ba\u53ef\u80fd\u6703\u8b8a\u5f97\u8907\u96dc\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5728\u6578\u64da\u5eab\u6392\u5e8f\u4e2d\u5982\u4f55\u8655\u7406 <code>NULL<\/code> \u503c\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u793a\u4f8b\u548c\u5efa\u8b70\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afnull%e5%80%bc%ef%bc%9f-sFhgCTAuoW\">\u4ec0\u9ebc\u662fNULL\u503c\uff1f<\/h2>\n<p><code>NULL<\/code> \u503c\u5728\u6578\u64da\u5eab\u4e2d\u8868\u793a\u7f3a\u5931\u6216\u672a\u77e5\u7684\u6578\u64da\u3002\u5b83\u4e0d\u540c\u65bc\u96f6\u6216\u7a7a\u5b57\u7b26\u4e32\uff0c\u56e0\u70ba\u9019\u4e9b\u503c\u662f\u5177\u9ad4\u7684\uff0c\u800c <code>NULL<\/code> \u5247\u8868\u793a\u201c\u6c92\u6709\u503c\u201d\u3002\u5728\u9032\u884c\u6392\u5e8f\u6642\uff0c\u6578\u64da\u5eab\u7cfb\u7d71\u9700\u8981\u660e\u78ba\u5982\u4f55\u8655\u7406\u9019\u4e9b <code>NULL<\/code> \u503c\uff0c\u4ee5\u78ba\u4fdd\u67e5\u8a62\u7d50\u679c\u7684\u6b63\u78ba\u6027\u548c\u4e00\u81f4\u6027\u3002<\/p>\n<h2 id=\"null%e5%80%bc%e7%9a%84%e6%8e%92%e5%ba%8f%e8%a1%8c%e7%82%ba-sFhgCTAuoW\">NULL\u503c\u7684\u6392\u5e8f\u884c\u70ba<\/h2>\n<p>\u5728\u5927\u591a\u6578\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\uff0c<code>NULL<\/code> \u503c\u7684\u6392\u5e8f\u884c\u70ba\u901a\u5e38\u9075\u5faa\u4ee5\u4e0b\u898f\u5247\uff1a<\/p>\n<ul>\n<li>\u5728\u5347\u5e8f\u6392\u5e8f\u4e2d\uff0c<code>NULL<\/code> \u503c\u901a\u5e38\u88ab\u8996\u70ba\u6700\u5c0f\u503c\uff0c\u6392\u5728\u6700\u524d\u9762\u3002<\/li>\n<li>\u5728\u964d\u5e8f\u6392\u5e8f\u4e2d\uff0c<code>NULL<\/code> \u503c\u5247\u88ab\u8996\u70ba\u6700\u5927\u503c\uff0c\u6392\u5728\u6700\u5f8c\u9762\u3002<\/li>\n<\/ul>\n<p>\u9019\u4e9b\u884c\u70ba\u53ef\u80fd\u6703\u56e0\u6578\u64da\u5eab\u7cfb\u7d71\u7684\u4e0d\u540c\u800c\u6709\u6240\u8b8a\u5316\uff0c\u56e0\u6b64\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c\u958b\u767c\u8005\u61c9\u8a72\u67e5\u95b1\u76f8\u95dc\u6587\u6a94\u4ee5\u4e86\u89e3\u5177\u9ad4\u7684\u6392\u5e8f\u898f\u5247\u3002<\/p>\n<h2 id=\"%e5%a6%82%e4%bd%95%e8%87%aa%e5%ae%9a%e7%be%a9null%e5%80%bc%e7%9a%84%e6%8e%92%e5%ba%8f-sFhgCTAuoW\">\u5982\u4f55\u81ea\u5b9a\u7fa9NULL\u503c\u7684\u6392\u5e8f<\/h2>\n<p>\u5982\u679c\u958b\u767c\u8005\u5e0c\u671b\u81ea\u5b9a\u7fa9 <code>NULL<\/code> \u503c\u7684\u6392\u5e8f\u884c\u70ba\uff0c\u53ef\u4ee5\u4f7f\u7528 SQL \u8a9e\u53e5\u4e2d\u7684 <code>ORDER BY<\/code> \u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u793a\u4f8b\uff1a<\/p>\n<h3 id=\"%e7%a4%ba%e4%be%8b1%ef%bc%9a%e5%8d%87%e5%ba%8f%e6%8e%92%e5%ba%8f%ef%bc%8cnull%e5%80%bc%e6%8e%92%e5%9c%a8%e6%9c%80%e5%be%8c-sFhgCTAuoW\">\u793a\u4f8b1\uff1a\u5347\u5e8f\u6392\u5e8f\uff0cNULL\u503c\u6392\u5728\u6700\u5f8c<\/h3>\n<pre><code>SELECT * FROM your_table\nORDER BY your_column ASC NULLS LAST;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u793a\u4f8b\u4e2d\uff0c\u67e5\u8a62\u5c07\u8fd4\u56de <code>your_table<\/code> \u4e2d\u7684\u6240\u6709\u884c\uff0c\u4e26\u6309\u7167 <code>your_column<\/code> \u7684\u503c\u9032\u884c\u5347\u5e8f\u6392\u5e8f\uff0c\u540c\u6642\u5c07 <code>NULL<\/code> \u503c\u6392\u5728\u6700\u5f8c\u3002<\/p>\n<h3 id=\"%e7%a4%ba%e4%be%8b2%ef%bc%9a%e9%99%8d%e5%ba%8f%e6%8e%92%e5%ba%8f%ef%bc%8cnull%e5%80%bc%e6%8e%92%e5%9c%a8%e6%9c%80%e5%89%8d-sFhgCTAuoW\">\u793a\u4f8b2\uff1a\u964d\u5e8f\u6392\u5e8f\uff0cNULL\u503c\u6392\u5728\u6700\u524d<\/h3>\n<pre><code>SELECT * FROM your_table\nORDER BY your_column DESC NULLS FIRST;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de <code>your_table<\/code> \u4e2d\u7684\u6240\u6709\u884c\uff0c\u4e26\u6309\u7167 <code>your_column<\/code> \u7684\u503c\u9032\u884c\u964d\u5e8f\u6392\u5e8f\uff0c\u5c07 <code>NULL<\/code> \u503c\u6392\u5728\u6700\u524d\u3002<\/p>\n<h2 id=\"%e8%80%83%e6%85%aenull%e5%80%bc%e7%9a%84%e5%bd%b1%e9%9f%bf-sFhgCTAuoW\">\u8003\u616eNULL\u503c\u7684\u5f71\u97ff<\/h2>\n<p>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u548c\u64b0\u5beb\u67e5\u8a62\u6642\uff0c\u958b\u767c\u8005\u61c9\u8a72\u8003\u616e <code>NULL<\/code> \u503c\u5c0d\u6578\u64da\u5b8c\u6574\u6027\u548c\u67e5\u8a62\u6027\u80fd\u7684\u5f71\u97ff\u3002\u904e\u591a\u7684 <code>NULL<\/code> \u503c\u53ef\u80fd\u6703\u5c0e\u81f4\u67e5\u8a62\u7d50\u679c\u4e0d\u6e96\u78ba\uff0c\u4e26\u5f71\u97ff\u6578\u64da\u5206\u6790\u7684\u7d50\u679c\u3002\u56e0\u6b64\uff0c\u5728\u6578\u64da\u63d2\u5165\u548c\u66f4\u65b0\u6642\uff0c\u61c9\u8a72\u8b39\u614e\u8655\u7406 <code>NULL<\/code> \u503c\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-sFhgCTAuoW\">\u7d50\u8ad6<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u6392\u5e8f\u4e2d\uff0c<code>NULL<\/code> \u503c\u7684\u8655\u7406\u662f\u4e00\u500b\u91cd\u8981\u7684\u8ab2\u984c\u3002\u4e86\u89e3\u5982\u4f55\u6b63\u78ba\u5730\u6392\u5e8f <code>NULL<\/code> \u503c\uff0c\u4e26\u6839\u64da\u9700\u6c42\u81ea\u5b9a\u7fa9\u6392\u5e8f\u884c\u70ba\uff0c\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u63d0\u9ad8\u67e5\u8a62\u7684\u6e96\u78ba\u6027\u548c\u6548\u7387\u3002\u7121\u8ad6\u662f\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u9084\u662f\u64b0\u5beb\u67e5\u8a62\u6642\uff0c\u5c0d <code>NULL<\/code> \u503c\u7684\u6b63\u78ba\u8655\u7406\u90fd\u662f\u4e0d\u53ef\u6216\u7f3a\u7684\u4e00\u90e8\u5206\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6216\u5176\u4ed6\u6280\u8853\u554f\u984c\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\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\">VPS<\/a> \u670d\u52d9\uff0c\u70ba\u60a8\u7684\u696d\u52d9\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u5728\u6578\u64da\u5eab\u6392\u5e8f\u4e2d\u5982\u4f55\u6709\u6548\u8655\u7406null\u503c\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u6e96\u78ba\u6027\u548c\u5b8c\u6574\u6027\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\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-153963","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/153963","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=153963"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/153963\/revisions"}],"predecessor-version":[{"id":153964,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/153963\/revisions\/153964"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=153963"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=153963"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=153963"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}