{"id":152957,"date":"2024-11-02T03:26:18","date_gmt":"2024-11-01T19:26:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/152957\/"},"modified":"2024-11-02T03:26:19","modified_gmt":"2024-11-01T19:26:19","slug":"%e8%99%95%e7%90%86-mssql-%e4%b8%ad%e7%9a%84%e7%a9%ba%e5%80%bc%ef%bc%9a%e5%88%a9%e7%94%a8-ifnull-%e5%87%bd%e6%95%b8%ef%bc%88mssql-%e4%b8%ad-ifnull%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/152957\/","title":{"rendered":"\u8655\u7406 MSSQL \u4e2d\u7684\u7a7a\u503c\uff1a\u5229\u7528 IFNULL \u51fd\u6578\uff08MSSQL \u4e2d IFNULL\uff09"},"content":{"rendered":"<h1 id=\"%e8%99%95%e7%90%86-mssql-%e4%b8%ad%e7%9a%84%e7%a9%ba%e5%80%bc%ef%bc%9a%e5%88%a9%e7%94%a8-ifnull-%e5%87%bd%e6%95%b8%ef%bc%88mssql-%e4%b8%ad-ifnull%ef%bc%89-NWhuZwlyej\">\u8655\u7406 MSSQL \u4e2d\u7684\u7a7a\u503c\uff1a\u5229\u7528 IFNULL \u51fd\u6578\uff08MSSQL \u4e2d IFNULL\uff09<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u4e2d\uff0c\u7a7a\u503c\uff08NULL\uff09\u662f\u4e00\u500b\u5e38\u898b\u7684\u554f\u984c\uff0c\u7279\u5225\u662f\u5728\u4f7f\u7528 Microsoft SQL Server\uff08MSSQL\uff09\u6642\u3002\u7a7a\u503c\u4ee3\u8868\u8457\u7f3a\u5931\u7684\u6578\u64da\uff0c\u9019\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u7d50\u679c\u548c\u6578\u64da\u7684\u5b8c\u6574\u6027\u3002\u70ba\u4e86\u6709\u6548\u5730\u8655\u7406\u7a7a\u503c\uff0cMSSQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u51fd\u6578\uff0c\u5176\u4e2d\u4e4b\u4e00\u5c31\u662f IFNULL \u51fd\u6578\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e IFNULL \u51fd\u6578\u7684\u4f7f\u7528\u65b9\u6cd5\u53ca\u5176\u5728\u8655\u7406\u7a7a\u503c\u6642\u7684\u61c9\u7528\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af-ifnull-%e5%87%bd%e6%95%b8%ef%bc%9f-NWhuZwlyej\">\u4ec0\u9ebc\u662f IFNULL \u51fd\u6578\uff1f<\/h2>\n<p>IFNULL \u51fd\u6578\u662f\u4e00\u500b\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u8868\u9054\u5f0f\u662f\u5426\u70ba\u7a7a\u503c\u7684\u51fd\u6578\u3002\u5982\u679c\u8a72\u8868\u9054\u5f0f\u70ba\u7a7a\u503c\uff0c\u5247\u8fd4\u56de\u6307\u5b9a\u7684\u66ff\u4ee3\u503c\uff1b\u5982\u679c\u4e0d\u662f\u7a7a\u503c\uff0c\u5247\u8fd4\u56de\u8a72\u8868\u9054\u5f0f\u7684\u539f\u59cb\u503c\u3002\u5728 MSSQL \u4e2d\uff0cIFNULL \u51fd\u6578\u7684\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>IFNULL(expression, replacement_value)<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>expression<\/code> \u662f\u8981\u6aa2\u67e5\u7684\u8868\u9054\u5f0f\uff0c\u800c <code>replacement_value<\/code> \u662f\u7576 <code>expression<\/code> \u70ba\u7a7a\u503c\u6642\u6240\u8fd4\u56de\u7684\u503c\u3002<\/p>\n<h2 id=\"ifnull-%e5%87%bd%e6%95%b8%e7%9a%84%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-NWhuZwlyej\">IFNULL \u51fd\u6578\u7684\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528 IFNULL \u51fd\u6578\u7684\u7bc4\u4f8b\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>Employees<\/code> \u7684\u8868\u683c\uff0c\u5176\u4e2d\u5305\u542b\u54e1\u5de5\u7684\u59d3\u540d\u548c\u85aa\u6c34\u3002\u67d0\u4e9b\u54e1\u5de5\u7684\u85aa\u6c34\u53ef\u80fd\u70ba\u7a7a\u503c\uff0c\u6211\u5011\u5e0c\u671b\u5728\u67e5\u8a62\u4e2d\u5c07\u9019\u4e9b\u7a7a\u503c\u66ff\u63db\u70ba 0\u3002<\/p>\n<pre><code>SELECT Name, IFNULL(Salary, 0) AS Salary\nFROM Employees;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u7576 <code>Salary<\/code> \u70ba\u7a7a\u503c\u6642\uff0c\u67e5\u8a62\u5c07\u8fd4\u56de 0\uff0c\u800c\u4e0d\u662f NULL\u3002\u9019\u6a23\u53ef\u4ee5\u78ba\u4fdd\u5728\u9032\u884c\u8a08\u7b97\u6216\u986f\u793a\u6578\u64da\u6642\u4e0d\u6703\u51fa\u73fe\u610f\u5916\u7684\u7a7a\u503c\u3002<\/p>\n<h2 id=\"ifnull-%e8%88%87%e5%85%b6%e4%bb%96%e5%87%bd%e6%95%b8%e7%9a%84%e6%af%94%e8%bc%83-NWhuZwlyej\">IFNULL \u8207\u5176\u4ed6\u51fd\u6578\u7684\u6bd4\u8f03<\/h2>\n<p>\u9664\u4e86 IFNULL \u51fd\u6578\uff0cMSSQL \u9084\u63d0\u4f9b\u4e86\u5176\u4ed6\u8655\u7406\u7a7a\u503c\u7684\u51fd\u6578\uff0c\u4f8b\u5982 <code>COALESCE<\/code> \u548c <code>ISNULL<\/code>\u3002\u9019\u4e9b\u51fd\u6578\u7684\u529f\u80fd\u985e\u4f3c\uff0c\u4f46\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002<\/p>\n<ul>\n<li><strong>COALESCE<\/strong>\uff1a\u9019\u500b\u51fd\u6578\u53ef\u4ee5\u63a5\u53d7\u591a\u500b\u53c3\u6578\uff0c\u4e26\u8fd4\u56de\u7b2c\u4e00\u500b\u975e\u7a7a\u503c\u3002\u4f8b\u5982\uff1a<\/li>\n<pre><code>SELECT COALESCE(Salary, Bonus, 0) AS TotalPay\n    FROM Employees;<\/code><\/pre>\n<li><strong>ISNULL<\/strong>\uff1a\u9019\u500b\u51fd\u6578\u50c5\u63a5\u53d7\u5169\u500b\u53c3\u6578\uff0c\u4e26\u8fd4\u56de\u7b2c\u4e00\u500b\u53c3\u6578\u7684\u503c\uff0c\u9664\u975e\u5b83\u662f\u7a7a\u503c\uff0c\u5247\u8fd4\u56de\u7b2c\u4e8c\u500b\u53c3\u6578\u3002\u4f8b\u5982\uff1a<\/li>\n<pre><code>SELECT ISNULL(Salary, 0) AS Salary\n    FROM Employees;<\/code><\/pre>\n<\/ul>\n<p>\u6839\u64da\u5177\u9ad4\u9700\u6c42\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u9078\u64c7\u6700\u9069\u5408\u7684\u51fd\u6578\u4f86\u8655\u7406\u7a7a\u503c\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-NWhuZwlyej\">\u7d50\u8ad6<\/h2>\n<p>\u5728 MSSQL \u4e2d\uff0c\u8655\u7406\u7a7a\u503c\u662f\u4e00\u500b\u91cd\u8981\u7684\u4efb\u52d9\uff0cIFNULL \u51fd\u6578\u63d0\u4f9b\u4e86\u4e00\u7a2e\u7c21\u55ae\u800c\u6709\u6548\u7684\u65b9\u6cd5\u4f86\u66ff\u4ee3\u7a7a\u503c\u3002\u901a\u904e\u4f7f\u7528 IFNULL \u51fd\u6578\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u78ba\u4fdd\u67e5\u8a62\u7d50\u679c\u7684\u5b8c\u6574\u6027\uff0c\u4e26\u907f\u514d\u56e0\u7a7a\u503c\u800c\u5c0e\u81f4\u7684\u8a08\u7b97\u932f\u8aa4\u3002\u7121\u8ad6\u662f\u7528\u65bc\u5831\u544a\u3001\u6578\u64da\u5206\u6790\u9084\u662f\u61c9\u7528\u7a0b\u5e8f\u958b\u767c\uff0c\u6b63\u78ba\u8655\u7406\u7a7a\u503c\u90fd\u662f\u78ba\u4fdd\u6578\u64da\u8cea\u91cf\u7684\u95dc\u9375\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\u4f86\u652f\u6301\u60a8\u7684 MSSQL \u6578\u64da\u5eab\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u4e0d\u540c\u9700\u6c42\u7684\u5ba2\u6236\u3002\u7121\u8ad6\u662f <a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u9084\u662f\u5176\u4ed6\u96f2\u670d\u52d9\uff0c\u6211\u5011\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u5982\u4f55\u5728 MSSQL \u4e2d\u4f7f\u7528 IFNULL \u51fd\u6578\u6709\u6548\u8655\u7406\u7a7a\u503c\uff0c\u78ba\u4fdd\u6578\u64da\u5b8c\u6574\u6027\u8207\u67e5\u8a62\u6e96\u78ba\u6027\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-152957","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/152957","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=152957"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/152957\/revisions"}],"predecessor-version":[{"id":152958,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/152957\/revisions\/152958"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=152957"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=152957"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=152957"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}