{"id":202513,"date":"2025-05-21T09:46:04","date_gmt":"2025-05-21T01:46:04","guid":{"rendered":"https:\/\/server.hk\/cnblog\/?p=202513"},"modified":"2025-05-21T09:46:04","modified_gmt":"2025-05-21T01:46:04","slug":"sql%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b0%e8%af%a6%e8%a7%a3%e4%b8%8e%e5%ae%9e%e6%88%98%ef%bc%9aavg%e3%80%81sum%e3%80%81count%e7%ad%89%e5%ba%94%e7%94%a8%e8%a7%a3%e6%9e%90","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/202513\/","title":{"rendered":"SQL\u805a\u5408\u51fd\u6570\u8be6\u89e3\u4e0e\u5b9e\u6218\uff1aAVG\u3001SUM\u3001COUNT\u7b49\u5e94\u7528\u89e3\u6790"},"content":{"rendered":"<h3>\u524d\u8a00<\/h3>\n<p>\u5728\u6570\u636e\u5e93\u64cd\u4f5c\u4e2d\uff0cSQL\u805a\u5408\u51fd\u6570\uff08Aggregate Functions\uff09\u662f\u5206\u6790\u548c\u5904\u7406\u5927\u91cf\u6570\u636e\u65f6\u4e0d\u53ef\u6216\u7f3a\u7684\u91cd\u8981\u5de5\u5177\u3002\u8fd9\u7c7b\u51fd\u6570\u901a\u5e38\u5728\u6570\u636e\u67e5\u8be2\u4e2d\u5bf9\u591a\u4e2a\u503c\u8fdb\u884c\u6c47\u603b\u3001\u7edf\u8ba1\u3001\u6c42\u5e73\u5747\u7b49\u8fd0\u7b97\uff0c\u4ece\u800c\u5e2e\u52a9\u6211\u4eec\u5feb\u901f\u6d1e\u5bdf\u6570\u636e\u80cc\u540e\u7684\u4ef7\u503c\u3002\u7279\u522b\u662f\u5728\u6784\u5efa\u9ad8\u6027\u80fd\u7684\u6570\u636e\u67e5\u8be2\u903b\u8f91\u65f6\uff0c\u805a\u5408\u51fd\u6570\u7684\u4f7f\u7528\u53ef\u4ee5\u663e\u8457\u63d0\u5347\u6548\u7387\u548c\u51c6\u786e\u6027\u3002<\/p>\n<p>\u672c\u6587\u5c06\u6df1\u5165\u89e3\u6790 SQL \u805a\u5408\u51fd\u6570\u7684\u7528\u6cd5\u53ca\u5b9e\u6218\u6848\u4f8b\uff0c\u9002\u7528\u4e8e\u6280\u672f\u4eba\u5458\u548c\u4f01\u4e1a\u5728\u9999\u6e2f\u90e8\u7f72\u6570\u636e\u670d\u52a1\u65f6\u4f18\u5316\u6570\u636e\u5e93\u6027\u80fd\uff0c\u5c24\u5176\u9002\u5408\u4f7f\u7528\u9ad8\u5e26\u5bbd\u3001\u9ad8\u53ef\u7528\u6027\u7684<strong>\u9999\u6e2f\u4e91\u670d\u52a1\u5668<\/strong>\u8fdb\u884c\u6570\u636e\u5bc6\u96c6\u578b\u4e1a\u52a1\u90e8\u7f72\u3002<\/p>\n<hr \/>\n<h3>\u4e00\u3001SQL\u805a\u5408\u51fd\u6570\u6982\u8ff0<\/h3>\n<p>SQL \u63d0\u4f9b\u4e86\u591a\u79cd\u805a\u5408\u51fd\u6570\uff0c\u5e38\u89c1\u7684\u6709\u4ee5\u4e0b\u51e0\u79cd\uff1a<\/p>\n<ul>\n<li><code>AVG()<\/code>\uff1a\u8fd4\u56de\u67d0\u5217\u7684\u5e73\u5747\u503c<\/li>\n<li><code>MIN()<\/code>\uff1a\u8fd4\u56de\u67d0\u5217\u4e2d\u7684\u6700\u5c0f\u503c<\/li>\n<li><code>MAX()<\/code>\uff1a\u8fd4\u56de\u67d0\u5217\u4e2d\u7684\u6700\u5927\u503c<\/li>\n<li><code>SUM()<\/code>\uff1a\u5bf9\u67d0\u5217\u503c\u6c42\u548c<\/li>\n<li><code>COUNT()<\/code>\uff1a\u7edf\u8ba1\u67d0\u5217\u6216\u6240\u6709\u8bb0\u5f55\u7684\u6570\u91cf<\/li>\n<\/ul>\n<p><strong>\u8bed\u6cd5\u683c\u5f0f<\/strong>\uff1a<\/p>\n<pre><code class=\"language-sql\">aggregate_function ([DISTINCT|ALL] expression)\r\n<\/code><\/pre>\n<ul>\n<li><code>DISTINCT<\/code>\uff1a\u53ea\u8ba1\u7b97\u552f\u4e00\u503c<\/li>\n<li><code>ALL<\/code>\uff1a\u9ed8\u8ba4\u884c\u4e3a\uff0c\u8ba1\u7b97\u6240\u6709\u503c\uff08\u5305\u62ec\u91cd\u590d\uff09<\/li>\n<\/ul>\n<hr \/>\n<h3>\u4e8c\u3001\u805a\u5408\u51fd\u6570\u793a\u4f8b\u5206\u6790<\/h3>\n<p>\u4e3a\u4fbf\u4e8e\u7406\u89e3\uff0c\u5047\u8bbe\u6709\u5982\u4e0b\u6570\u636e\u8868 <code>Details<\/code>\uff1a<\/p>\n<table>\n<thead>\n<tr>\n<th>ID<\/th>\n<th>Name<\/th>\n<th>Amount<\/th>\n<th>Age<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>Safa<\/td>\n<td>5000<\/td>\n<td>21<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>Aman<\/td>\n<td>2500<\/td>\n<td>23<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>Rehaan<\/td>\n<td>20000<\/td>\n<td>25<\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>Seema<\/td>\n<td>12000<\/td>\n<td>25<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h4>1. <code>AVG()<\/code> \u51fd\u6570\uff1a\u5e73\u5747\u503c\u8ba1\u7b97<\/h4>\n<pre><code class=\"language-sql\">SELECT AVG(Amount) FROM Details;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a9875\r\n<\/code><\/pre>\n<p>\u8fd9\u4e2a\u51fd\u6570\u4f1a\u8fd4\u56de <code>Amount<\/code> \u5b57\u6bb5\u6240\u6709\u8bb0\u5f55\u7684\u5e73\u5747\u503c\uff0c\u9002\u7528\u4e8e\u6570\u636e\u8bc4\u4f30\u548c\u4ef7\u683c\u5206\u6790\u573a\u666f\u3002<\/p>\n<h4>2. <code>MIN()<\/code> \u51fd\u6570\uff1a\u6700\u5c0f\u503c\u67e5\u8be2<\/h4>\n<pre><code class=\"language-sql\">SELECT MIN(Amount) FROM Details;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a2500\r\n<\/code><\/pre>\n<p>\u7528\u4e8e\u627e\u51fa\u67d0\u5217\u4e2d\u6700\u5c0f\u7684\u6570\u503c\uff0c\u9002\u7528\u4e8e\u7b5b\u9009\u6700\u4f4e\u9500\u552e\u989d\u7b49\u4e1a\u52a1\u573a\u666f\u3002<\/p>\n<h4>3. <code>MAX()<\/code> \u51fd\u6570\uff1a\u6700\u5927\u503c\u67e5\u8be2<\/h4>\n<pre><code class=\"language-sql\">SELECT MAX(Amount) FROM Details;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a20000\r\n<\/code><\/pre>\n<p>\u540c\u7406\uff0cMAX \u51fd\u6570\u7528\u4e8e\u67e5\u627e\u6700\u5927\u503c\uff0c\u5e38\u7528\u4e8e\u6536\u5165\u7edf\u8ba1\u3001\u6d41\u91cf\u5cf0\u503c\u7b49\u5206\u6790\u4efb\u52a1\u3002<\/p>\n<h4>4. <code>SUM()<\/code> \u51fd\u6570\uff1a\u603b\u548c\u7edf\u8ba1<\/h4>\n<pre><code class=\"language-sql\">SELECT SUM(Amount) FROM Details;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a39500\r\n<\/code><\/pre>\n<p>\u8be5\u51fd\u6570\u5e7f\u6cdb\u5e94\u7528\u4e8e\u9500\u552e\u603b\u989d\u3001\u8d44\u6e90\u603b\u91cf\u7b49\u573a\u666f\uff0c\u9002\u7528\u4e8e\u4e1a\u52a1\u6570\u636e\u6c47\u603b\u3002<\/p>\n<h5>\u4f7f\u7528 <code>GROUP BY<\/code> \u642d\u914d <code>SUM()<\/code> \u7684\u67e5\u8be2\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT SUM(Amount), Name FROM Details WHERE Age &gt; 21 GROUP BY Name;\r\n<\/code><\/pre>\n<p>\u4e0a\u8ff0\u8bed\u53e5\u6839\u636e <code>Name<\/code> \u5206\u7ec4\u7edf\u8ba1 <code>Amount<\/code> \u603b\u548c\u3002<\/p>\n<h5>\u642d\u914d <code>HAVING<\/code> \u6761\u4ef6\u8fc7\u6ee4\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT SUM(Amount), Name FROM Details GROUP BY Name HAVING SUM(Amount) &gt; 2500;\r\n<\/code><\/pre>\n<p>\u53ef\u4ee5\u7b5b\u9009\u51fa\u9500\u552e\u989d\u8d85\u8fc7\u67d0\u4e00\u9608\u503c\u7684\u4eba\u5458\u3002<\/p>\n<h4>5. <code>COUNT()<\/code> \u51fd\u6570\uff1a\u6570\u91cf\u7edf\u8ba1<\/h4>\n<pre><code class=\"language-sql\">SELECT COUNT(Amount) FROM Details;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a4\r\n<\/code><\/pre>\n<p>\u8fd4\u56de\u67d0\u5217\u4e2d\u4e0d\u4e3a NULL \u7684\u8bb0\u5f55\u6570\uff0c\u9002\u7528\u4e8e\u8bb0\u5f55\u8ba1\u6570\u3001\u7528\u6237\u6d3b\u8dc3\u5ea6\u8bc4\u4f30\u7b49\u3002<\/p>\n<h5>\u7ed3\u5408 <code>*<\/code> \u7684\u5199\u6cd5\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT COUNT(*) FROM Details;\r\n-- \u8fd4\u56de\u6240\u6709\u884c\u6570\uff1a4\r\n<\/code><\/pre>\n<h5>\u52a0\u4e0a <code>WHERE<\/code> \u5b50\u53e5\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT COUNT(*) FROM Details WHERE Age &lt; 25;\r\n-- \u8fd4\u56de\u7ed3\u679c\uff1a2\r\n<\/code><\/pre>\n<h5>\u4f7f\u7528 <code>GROUP BY<\/code> \u7edf\u8ba1\u5206\u7c7b\u6570\u636e\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT COUNT(Amount), Name FROM Details WHERE Age &lt; 25 GROUP BY Name;\r\n<\/code><\/pre>\n<h5>\u4e0e <code>HAVING<\/code> \u8054\u5408\u4f7f\u7528\uff1a<\/h5>\n<pre><code class=\"language-sql\">SELECT COUNT(Amount), Age, Name FROM Details GROUP BY Name HAVING Age &gt;= 25;\r\n<\/code><\/pre>\n<hr \/>\n<h3>\u4e09\u3001\u5728\u9999\u6e2f\u670d\u52a1\u5668\u73af\u5883\u4e0b\u4f18\u5316\u805a\u5408\u51fd\u6570\u67e5\u8be2\u6027\u80fd<\/h3>\n<p>\u968f\u7740\u6570\u636e\u91cf\u7684\u589e\u52a0\uff0c\u6570\u636e\u5e93\u805a\u5408\u8fd0\u7b97\u5bf9\u8ba1\u7b97\u8d44\u6e90\u7684\u8981\u6c42\u4e5f\u968f\u4e4b\u63d0\u9ad8\u3002\u4e3a\u4e86\u4fdd\u8bc1\u9ad8\u6548\u5904\u7406 SQL \u805a\u5408\u67e5\u8be2\uff0c\u5efa\u8bae\u90e8\u7f72\u9ad8\u6027\u80fd\u3001\u4f4e\u5ef6\u8fdf\u7684\u8ba1\u7b97\u8d44\u6e90\u3002\u4f8b\u5982\u9009\u62e9<strong>\u9999\u6e2fvps<\/strong>\u6216<strong>\u9999\u6e2f\u72ec\u7acb\u670d\u52a1\u5668<\/strong>\uff0c\u80fd\u591f\u5927\u5e45\u63d0\u5347\u6570\u636e\u5e93\u54cd\u5e94\u901f\u5ea6\u548c\u6570\u636e\u541e\u5410\u80fd\u529b\uff0c\u7279\u522b\u9002\u5408\u5904\u7406\u9ad8\u5e76\u53d1\u6570\u636e\u67e5\u8be2\u4e1a\u52a1\u3002<\/p>\n<p>\u5229\u7528\u9999\u6e2f\u672c\u5730\u4f18\u8d28\u7f51\u7edc\u8d44\u6e90\u4e0e\u670d\u52a1\u5668\u786c\u4ef6\uff0c\u53ef\u4ee5\u6781\u5927\u63d0\u5347\u6570\u636e\u5e93\u67e5\u8be2\u7684\u7a33\u5b9a\u6027\u548c\u6574\u4f53\u8fd0\u7b97\u6548\u7387\u3002\u65e0\u8bba\u662f\u7535\u5546\u4e1a\u52a1\u3001\u8d22\u52a1\u6570\u636e\u5904\u7406\uff0c\u8fd8\u662f\u5927\u89c4\u6a21\u65e5\u5fd7\u7edf\u8ba1\uff0c\u914d\u5408\u5408\u9002\u7684\u6570\u636e\u5e93\u7d22\u5f15\u7b56\u7565\u4e0e\u805a\u5408\u51fd\u6570\u7ec4\u5408\uff0c\u90fd\u80fd\u5728\u6027\u80fd\u4e0e\u7a33\u5b9a\u6027\u4e4b\u95f4\u53d6\u5f97\u66f4\u4f18\u5e73\u8861\u3002<\/p>\n<hr \/>\n<h3>\u56db\u3001\u603b\u7ed3<\/h3>\n<p>SQL\u805a\u5408\u51fd\u6570\u4e3a\u5f00\u53d1\u8005\u63d0\u4f9b\u4e86\u5f3a\u5927\u4e14\u4fbf\u6377\u7684\u6570\u636e\u7edf\u8ba1\u4e0e\u5206\u6790\u624b\u6bb5\u3002\u5728\u5b9e\u9645\u5e94\u7528\u4e2d\uff0c\u5408\u7406\u4f7f\u7528 <code>AVG()<\/code>\u3001<code>SUM()<\/code>\u3001<code>COUNT()<\/code> \u7b49\u51fd\u6570\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u51cf\u5c11\u5e94\u7528\u5c42\u8ba1\u7b97\u8d1f\u62c5\uff0c\u4e5f\u80fd\u5927\u5e45\u63d0\u5347\u6570\u636e\u5904\u7406\u6548\u7387\u3002\u5bf9\u4e8e\u4f7f\u7528<a href=\"https:\/\/server.hk\/\"><strong>\u9999\u6e2f\u4e91\u670d\u52a1\u5668<\/strong><\/a>\u90e8\u7f72\u6570\u636e\u5e93\u670d\u52a1\u7684\u7528\u6237\u6765\u8bf4\uff0c\u8fd9\u4e9b\u805a\u5408\u67e5\u8be2\u4f18\u5316\u624b\u6bb5\u5c24\u5176\u91cd\u8981\u3002<\/p>\n<p>\u901a\u8fc7\u914d\u5408\u4f18\u8d28\u670d\u52a1\u5668\u8d44\u6e90\uff0c\u7528\u6237\u53ef\u4ee5\u66f4\u9ad8\u6548\u5730\u6784\u5efa\u7a33\u5b9a\u3001\u5b89\u5168\u3001\u9ad8\u6027\u80fd\u7684\u6570\u636e\u5e93\u7cfb\u7edf\uff0c\u6ee1\u8db3\u5404\u7c7b\u6570\u636e\u5bc6\u96c6\u578b\u5e94\u7528\u573a\u666f\u7684\u4e1a\u52a1\u9700\u6c42\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u524d\u8a00 \u5728\u6570\u636e\u5e93\u64cd\u4f5c\u4e2d\uff0cSQL\u805a\u5408&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-202513","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/202513","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=202513"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/202513\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=202513"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=202513"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=202513"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}