{"id":200334,"date":"2025-05-06T08:30:09","date_gmt":"2025-05-06T00:30:09","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200334\/"},"modified":"2025-05-06T08:30:09","modified_gmt":"2025-05-06T00:30:09","slug":"%e5%a6%82%e4%bd%95%e6%a0%b9%e6%8d%ae%e6%9d%a1%e4%bb%b6%e5%b0%86%e5%a4%9a%e4%b8%aa%e5%ad%97%e6%ae%b5%e7%bb%84%e5%90%88%e6%88%90%e6%96%b0%e5%ad%97%e6%ae%b5%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200334\/","title":{"rendered":"\u5982\u4f55\u6839\u636e\u6761\u4ef6\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57\u6bb5\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u5982\u4f55\u6839\u636e\u6761\u4ef6\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57\u6bb5\uff1f<\/h1>\n<p>IT\u884c\u4e1a\u76f8\u5bf9\u4e8e\u4e00\u822c\u4f20\u7edf\u884c\u4e1a\uff0c\u53d1\u5c55\u66f4\u65b0\u901f\u5ea6\u66f4\u5feb\uff0c\u4e00\u65e6\u505c\u6b62\u4e86\u5b66\u4e60\uff0c\u5f88\u5feb\u5c31\u4f1a\u88ab\u884c\u4e1a\u6240\u6dd8\u6c70\u3002\u6240\u4ee5\u6211\u4eec\u9700\u8981\u8e0f\u8e0f\u5b9e\u5b9e\u7684\u4e0d\u65ad\u5b66\u4e60\uff0c\u7cbe\u8fdb\u81ea\u5df1\u7684\u6280\u672f\uff0c\u5c24\u5176\u662f\u521d\u5b66\u8005\u3002\u4eca\u5929\u4e3b\u673a\u5b9d\u8d1d\u7ed9\u5927\u5bb6\u6574\u7406\u4e86\u300a\u5982\u4f55\u6839\u636e\u6761\u4ef6\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57\u6bb5\uff1f\u300b\uff0c\u804a\u804a\uff0c\u6211\u4eec\u4e00\u8d77\u6765\u770b\u770b\u5427\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241102\/173051033167257dfbe77b0.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>\u5982\u4f55\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57\u6bb5\uff1f<\/strong><\/p>\n<p>\u8003\u8651\u4e00\u4e2a\u5305\u542b\u4ee5\u4e0b\u6570\u636e\u7684\u8868\uff1a<\/p>\n<pre>+------+---------+---------+\n| id   | \u4ef7\u683c1   | \u4ef7\u683c2   |\n+------+---------+---------+\n| 1    | 3.5     | 3.6     |\n| 2    | 2.1     | null    |\n| 3    | 2.35    | 2       |\n| 4    | 3.2     | null    |\n+------+---------+---------+<\/pre>\n<p><strong>\u9700\u6c42\uff1a<\/strong>\u5b9a\u4e49 &lt;\u4ef7\u683c&gt; \u5b57\u6bb5\uff0c\u89c4\u5219\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u5982\u679c\u6709 &lt;\u4ef7\u683c2&gt;\uff0c\u5219 &lt;\u4ef7\u683c&gt; \u7b49\u4e8e &lt;\u4ef7\u683c2&gt;\u3002<\/li>\n<li>\u5426\u5219 &lt;\u4ef7\u683c&gt; \u7b49\u4e8e &lt;\u4ef7\u683c1&gt;\u3002<\/li>\n<\/ul>\n<p><strong>\u5982\u4f55\u5b9e\u73b0\uff1f<\/strong><\/p>\n<p>\u4f7f\u7528\u4ee5\u4e0b sql \u67e5\u8be2\u83b7\u53d6 &lt;\u4ef7\u683c&gt; \u5b57\u6bb5\uff1a<\/p>\n<pre>select id, if (\u4ef7\u683c2 is not null, \u4ef7\u683c2\uff0c\u4ef7\u683c1) as price<\/pre>\n<p><strong>\u89e3\u6790\uff1a<\/strong><\/p>\n<ul>\n<li>if() \u51fd\u6570\u7528\u4e8e\u6839\u636e\u6761\u4ef6\u5224\u65ad\u548c\u8fd4\u56de\u4e0d\u540c\u503c\u3002<\/li>\n<li>if (\u4ef7\u683c2 is not null, \u4ef7\u683c2\uff0c\u4ef7\u683c1)\uff1a\u5982\u679c &lt;\u4ef7\u683c2&gt; \u4e0d\u4e3a null\uff0c\u5219\u8fd4\u56de &lt;\u4ef7\u683c2&gt;\uff1b\u5426\u5219\u8fd4\u56de &lt;\u4ef7\u683c1&gt;\u3002<\/li>\n<\/ul>\n<p><strong>\u7ed3\u679c\uff1a<\/strong><\/p>\n<pre>+---------+-----+\n| ID   | \u4ef7\u683c |\n+---------+-----+\n| 1    | 3.6 |\n| 2    | 2.1 |\n| 3    | 2   |\n| 4    | 3.2 |\n+---------+-----+<\/pre>\n<p>\u4ee5\u4e0a\u5c31\u662f\u300a\u5982\u4f55\u6839\u636e\u6761\u4ef6\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57\u6bb5\uff1f\u300b\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u5173\u4e8e\u7684\u8d44\u6599\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u4f55\u6839\u636e\u6761\u4ef6\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u65b0\u5b57&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200334","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200334","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200334"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200334\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200334"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200334"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200334"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}