{"id":224882,"date":"2021-09-04T08:47:54","date_gmt":"2021-09-04T00:47:54","guid":{"rendered":"https:\/\/lrxjmw.cn\/?p=224882"},"modified":"2021-08-23T08:48:35","modified_gmt":"2021-08-23T00:48:35","slug":"sql-handle-0","status":"publish","type":"post","link":"https:\/\/lrxjmw.cn\/sql-handle-0.html","title":{"rendered":"SQL\u4e2d\u9664\u6570\u4e3a0\u5904\u7406\u60c5\u51b5\u6f14\u793a"},"content":{"rendered":"<table>\n<tbody>\n<tr>\n<td style=\"padding: 5px 12px; width: 25px; font-size: 22px; text-align: center; background: #E8E8E8; line-height: 30px; color: #999;\">\u5bfc\u8bfb<\/td>\n<td style=\"padding: 10px 10px 12px; line-height: 20px;\"><strong>\u6211\u4eec\u5728\u8fdb\u884c\u6570\u636e\u7edf\u8ba1\u7684\u65f6\u5019\uff0c\u7ecf\u5e38\u4f1a\u9047\u5230\u6c42\u767e\u5206\u6bd4\uff0c\u73af\u6bd4\uff0c\u540c\u6bd4\u7b49\u8fd9\u4e9b\u9700\u8981\u9664\u4ee5\u67d0\u4e2a\u6570\u7684\u60c5\u51b5\uff0c\u800c\u5982\u679c\u9664\u6570\u4e3a0\uff0c\u6570\u636e\u5e93\u662f\u4f1a\u62a5\u9519\u7684\u3002\u90a3\u4e48\u9047\u5230\u8fd9\u6837\u7684\u60c5\u51b5\u6211\u4eec\u600e\u4e48\u5904\u7406\u5462?\u4e0b\u9762\u6211\u4eec\u7528\u793a\u4f8b\u7ed9\u5927\u5bb6\u8bb2\u89e3\u4e00\u4e0b\u5904\u7406\u65b9\u6cd5\u3002<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/lrxjmw.cn\/wp-content\/uploads\/2019\/12\/sql.jpg\" alt=\"\" width=\"500\" height=\"453\" class=\"alignnone size-full wp-image-166159\" srcset=\"https:\/\/lrxjmw.cn\/wp-content\/uploads\/2019\/12\/sql.jpg 500w, https:\/\/lrxjmw.cn\/wp-content\/uploads\/2019\/12\/sql-300x272.jpg 300w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<div   id="j6sjwn9j3u"    style=\"font-size: 14pt; color: white; background-color: black; border-left: red 10px solid; padding-left: 14px; margin-bottom: 20px; margin-top: 20px;\"><strong>\u60c5\u51b5\u4e00<\/strong><\/div>\n<p>\u4f8b\u5982<\/p>\n<pre>SELECT  A\/B  FROM TAB<\/pre>\n<p>\u9047\u5230\u8fd9\u6837\u7684\u60c5\u51b5\uff0c\u4e00\u822c\u7684\u5904\u7406\u65b9\u6cd5\u662f\u7528CASE WHEN\u6765\u5224\u65adB\u7684\u503c<\/p>\n<pre>SELECT  \r\nCASE WHEN B=0 THEN 0 ELSE A\/B END   \r\nFROM TAB <\/pre>\n<p>\u8fd9\u6837\u5f53B\u5982\u679c\u662f0\uff0c\u6211\u4eec\u76f4\u63a5\u8d4b\u4e00\u4e2a\u503c\uff0c\u907f\u514dA\/B\u53c2\u4e0e\u8ba1\u7b97\u62a5\u9519\u3002<\/p>\n<div   id="j6sjwn9j3u"    style=\"font-size: 14pt; color: white; background-color: black; border-left: red 10px solid; padding-left: 14px; margin-bottom: 20px; margin-top: 20px;\"><strong>\u60c5\u51b5\u4e8c<\/strong><\/div>\n<p>\u4e0a\u9762\u662f\u4e00\u79cd\u5e38\u89c1\u7684\u60c5\u51b5\uff0c\u4f46\u662f\u5982\u679c\u9047\u5230\u4e0b\u9762\u8fd9\u6837\u7684\u805a\u5408\u51fd\u6570\u5462?<\/p>\n<p>\u4f8b\u5982<\/p>\n<pre>SELECT  SUM(A)\/COUNT(B) FROM TAB<\/pre>\n<p>\u9047\u5230\u8fd9\u6837\u7684\u60c5\u51b5CASE WHEN \u662f\u4e0d\u80fd\u5224\u65adCOUNT(B)\u7684\u503c\u7684\uff0c\u56e0\u4e3aWHEN\u540e\u9762\u7684\u6761\u4ef6\u4e0d\u80fd\u4f7f\u7528\u805a\u5408\u51fd\u6570(\u8bed\u6cd5\u8981\u6c42)\uff0c\u8fd9\u4e2a\u65f6\u5019\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5904\u7406<\/p>\n<pre>SELECT   \r\nISNULL(SUM(A)\/NULLIF(COUNT(B),0),0)   \r\nFROM  TAB <\/pre>\n<p>\u5176\u4e2d\u8fd9\u91cc\u4f7f\u7528\u4e86\u4e24\u4e2a\u51fd\u6570\uff0cNULLIF()\u548cISNULL()<\/p>\n<p>NULLIF\u51fd\u6570\u6709\u4e24\u4e2a\u53c2\u6570,\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<p>NULLIF( expression1 , expression2 )<\/p>\n<p>\u5176\u4f5c\u7528\u5c31\u662f\uff1a\u5982\u679c\u4e24\u4e2a\u6307\u5b9a\u7684\u8868\u8fbe\u5f0f\u76f8\u7b49\uff0c\u5c31\u8fd4\u56deNULL\u503c\u3002<\/p>\n<p>ISNULL\u51fd\u6570\u4e5f\u6709\u4e24\u4e2a\u53c2\u6570\uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<p>ISNULL( expression1 , expression2 )<\/p>\n<p>\u5176\u4f5c\u7528\u662f\uff1a\u5982\u679c\u7b2c\u4e00\u4e2a\u53c2\u6570\u7684\u7ed3\u679c\u4e3aNULL\uff0c\u5c31\u8fd4\u56de\u7b2c\u4e8c\u4e2a\u53c2\u6570\u7684\u503c\u3002<\/p>\n<p>\u5f53COUNT(B)\u7684\u7ed3\u679c\u4e3a0\u65f6\uff0c\u6070\u597d\u4e0e\u7b2c\u4e8c\u4e2a\u7ed9\u5b9a\u7684\u53c2\u65700\u76f8\u7b49\uff0c\u8fd9\u4e2a\u65f6\u5019NULLIF\u51fd\u6570\u5c31\u4f1a\u8fd4\u56deNULL\uff0c\u800cSUM(A)\u5728\u9664\u4ee5NULL\u65f6\u7ed3\u679c\u4e3aNULL\uff0c\u5916\u5c42\u4f7f\u7528ISNULL\u51fd\u6570\u518d\u5bf9NULL\u503c\u8fdb\u884c\u5224\u65ad\uff0c\u8fd9\u6837\u6700\u7ec8\u7ed3\u679c\u5c31\u662f0\u4e86\u3002<\/p>\n<p>\u8fd9\u4e24\u79cd\u65b9\u6cd5\u5c31\u662f\u6211\u4eec\u65e5\u5e38\u5904\u7406\u9664\u6570\u4e3a0\u7684\u60c5\u51b5\u4e86\uff0c\u4e00\u5b9a\u8981\u8bb0\u5f97\u54e6\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4f8b\u5982 SELECT A\/B FROM TAB \u9047\u5230\u8fd9\u6837\u7684\u60c5\u51b5\uff0c\u4e00\u822c\u7684\u5904\u7406\u65b9\u6cd5\u662f\u7528CASE WHEN\u6765\u5224\u65adB\u7684\u503c [&hellip;]<\/p>\n","protected":false},"author":1920,"featured_media":208759,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[55],"tags":[],"class_list":["post-224882","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-thread"],"acf":[],"_links":{"self":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/224882","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/users\/1920"}],"replies":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/comments?post=224882"}],"version-history":[{"count":4,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/224882\/revisions"}],"predecessor-version":[{"id":225036,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/224882\/revisions\/225036"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/media\/208759"}],"wp:attachment":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/media?parent=224882"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/categories?post=224882"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/tags?post=224882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}