{"id":6947,"date":"2024-11-14T09:13:13","date_gmt":"2024-11-14T01:13:13","guid":{"rendered":"https:\/\/fwq.ai\/blog\/6947\/"},"modified":"2024-11-14T09:13:13","modified_gmt":"2024-11-14T01:13:13","slug":"%e5%a6%82%e4%bd%95%e7%94%a8-mysql-%e6%9f%a5%e8%af%a2%e5%b0%86%e5%a4%9a%e4%b8%aa%e5%ad%97%e6%ae%b5%e7%bb%84%e5%90%88%e6%88%90%e4%b8%80%e4%b8%aa%e6%96%b0%e5%ad%97%e6%ae%b5%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/6947\/","title":{"rendered":"\u5982\u4f55\u7528 MySQL \u67e5\u8be2\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\uff1f"},"content":{"rendered":"<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/001\/246\/273\/173016810386967.jpg\" class=\"aligncenter\" title=\"\u5982\u4f55\u7528 MySQL \u67e5\u8be2\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\uff1f\u63d2\u56fe\" alt=\"\u5982\u4f55\u7528 MySQL \u67e5\u8be2\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u4e3a\u65b0\u5b57\u6bb5\u7684  \u67e5\u8be2<\/strong><\/p>\n<p>\u5728\u67d0\u4e9b\u573a\u666f\u4e2d\uff0c\u6211\u4eec\u9700\u8981\u5c06\u8868\u4e2d\u7684\u591a\u4e2a\u5b57\u6bb5\u6309\u7167\u4e00\u5b9a\u7684\u89c4\u5219\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\u3002\u6bd4\u5982\uff0c\u4ee5\u4e0b\u8868\u6709\u4e24\u4e2a\u5b57\u6bb5\u201c\u4ef7\u683c1\u201d\u548c\u201c\u4ef7\u683c2\u201d\uff0c\u6211\u4eec\u9700\u8981\u57fa\u4e8e\u4e00\u5b9a\u7684\u89c4\u5219\u751f\u6210\u4e00\u4e2a\u540d\u4e3a\u201c\u4ef7\u683c\u201d\u7684\u65b0\u5b57\u6bb5\u3002<\/p>\n<pre>**\u8868\uff1a**\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  |<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>\u89c4\u5219\uff1a<\/strong><\/p>\n<ul>\n<li>\u5982\u679c\u201c\u4ef7\u683c2\u201d\u4e0d\u4e3a null\uff0c\u90a3\u4e48\u201c\u4ef7\u683c\u201d\u7b49\u4e8e\u201c\u4ef7\u683c2\u201d\u3002<\/li>\n<li>\u5982\u679c\u201c\u4ef7\u683c2\u201d\u4e3a null\uff0c\u90a3\u4e48\u201c\u4ef7\u683c\u201d\u7b49\u4e8e\u201c\u4ef7\u683c1\u201d\u3002<\/li>\n<\/ul>\n<p><strong>\u67e5\u8be2\uff1a<\/strong><\/p>\n<p>\u4e3a\u4e86\u751f\u6210\u201c\u4ef7\u683c\u201d\u5b57\u6bb5\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b mysql \u67e5\u8be2\uff1a<\/p>\n<pre>select id, if (\u4ef7\u683c2 is not null, \u4ef7\u683c2\uff0c\u4ef7\u683c1) as price<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>\u7ed3\u679c\uff1a<\/strong><\/p>\n<p>\u67e5\u8be2\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n<pre>| ID |    \u4ef7\u683c    |\n|---|---|\n| 1  |    3.6    |\n| 2  |    2.1    |\n| 3  |    2.00   |\n| 4  |    3.2    |<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u901a\u8fc7\u8fd9\u4e2a\u67e5\u8be2\uff0c\u6211\u4eec\u6210\u529f\u5730\u5c06\u201c\u4ef7\u683c1\u201d\u548c\u201c\u4ef7\u683c2\u201d\u5b57\u6bb5\u6309\u7167\u7279\u5b9a\u7684\u89c4\u5219\u7ec4\u5408\u6210\u4e86\u4e00\u4e2a\u540d\u4e3a\u201c\u4ef7\u683c\u201d\u7684\u65b0\u5b57\u6bb5\u3002\u8fd9\u5728\u5b9e\u9645\u5e94\u7528\u4e2d\u975e\u5e38\u6709\u7528\uff0c\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u4ece\u8868\u4e2d\u63d0\u53d6\u66f4\u590d\u6742\u7684\u4fe1\u606f\u3002<\/p>\n<p>\u4ee5\u4e0a\u5c31\u662f\u5982\u4f55\u7528 MySQL \u67e5\u8be2\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5c06\u591a\u4e2a\u5b57\u6bb5\u7ec4\u5408\u4e3a\u65b0\u5b57\u6bb5\u7684 \u67e5\u8be2 \u5728\u67d0\u4e9b\u573a\u666f\u4e2d\uff0c\u6211\u4eec\u9700\u8981\u5c06\u8868\u4e2d\u7684\u591a\u4e2a\u5b57\u6bb5\u6309\u7167\u4e00\u5b9a\u7684\u89c4\u5219\u7ec4\u5408\u6210\u4e00\u4e2a\u65b0\u5b57\u6bb5\u3002\u6bd4\u5982\uff0c\u4ee5\u4e0b\u8868\u6709\u4e24\u4e2a\u5b57\u6bb5\u201c\u4ef7\u683c1\u201d\u548c\u201c\u4ef7\u683c2\u201d\uff0c\u6211\u4eec\u9700\u8981\u57fa\u4e8e\u4e00\u5b9a\u7684\u89c4\u5219\u751f\u6210\u4e00\u4e2a\u540d\u4e3a\u201c\u4ef7\u683c\u201d\u7684\u65b0\u5b57\u6bb5\u3002 **\u8868\uff1a** | id | \u4ef7\u683c1 | \u4ef7\u683c2 | |&#8212;|&#8212;|&#8212;| | 1 | 3.5 | 3.6 | | 2 | 2.1 | null | | 3 | 2.35 | 2 | | 4 | 3.2 | null | \u767b\u5f55\u540e\u590d\u5236 \u89c4\u5219\uff1a \u5982\u679c\u201c\u4ef7\u683c2\u201d\u4e0d\u4e3a null\uff0c\u90a3\u4e48\u201c\u4ef7\u683c\u201d\u7b49\u4e8e\u201c\u4ef7\u683c2\u201d\u3002 \u5982\u679c\u201c\u4ef7\u683c2\u201d\u4e3a null\uff0c\u90a3\u4e48\u201c\u4ef7\u683c\u201d\u7b49\u4e8e\u201c\u4ef7\u683c1\u201d\u3002 \u67e5\u8be2\uff1a \u4e3a\u4e86\u751f\u6210\u201c\u4ef7\u683c\u201d\u5b57\u6bb5\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b mysql \u67e5\u8be2\uff1a select id, if (\u4ef7\u683c2 is [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-6947","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/6947","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=6947"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/6947\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=6947"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=6947"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=6947"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}