{"id":57863,"date":"2025-08-15T21:40:18","date_gmt":"2025-08-15T13:40:18","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/57863.html"},"modified":"2025-08-15T21:40:18","modified_gmt":"2025-08-15T13:40:18","slug":"%e4%b8%ba%e4%bb%80%e4%b9%88count%e5%88%97%e5%90%8d%e7%9a%84%e7%bb%93%e6%9e%9c%ef%bc%8c%e6%9c%89%e6%97%b6%e6%af%94count%e5%b0%91%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/57863.html","title":{"rendered":"\u4e3a\u4ec0\u4e48COUNT(\u5217\u540d)\u7684\u7ed3\u679c\uff0c\u6709\u65f6\u6bd4COUNT(*)\u5c11\uff1f"},"content":{"rendered":"<\/p>\n<p class=\"img-center\"><img loading=\"lazy\" decoding=\"async\" alt=\"\u56fe\u7247\" height=\"2337\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815134008-689f38b8b1102.png\" width=\"1080\" \/><\/p>\n<h3>\u7b2c\u4e00\u6b65&#xff1a;\u6280\u672f\u89e3\u6790\u4e0eSQL\u793a\u4f8b<\/h3>\n<h4>\u6838\u5fc3\u533a\u522b\u6982\u8ff0<\/h4>\n<ul>\n<li>\n<p>\u2022\u00a0count(*): \u7edf\u8ba1\u6240\u6709\u884c\u7684\u6570\u91cf\u3002\u5b83\u4e0d\u5173\u5fc3\u4efb\u4f55\u5217\u7684\u5185\u5bb9&#xff0c;\u53ea\u662f\u7b80\u5355\u5730\u8ba1\u7b97\u884c\u6570\u3002\u5b83\u4f1a\u5305\u542b\u503c\u4e3aNULL\u7684\u884c\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0count(1): \u4e0ecount(*)\u57fa\u672c\u7b49\u4ef7\u3002\u5b83\u4e3a\u6bcf\u4e00\u884c\u8ba1\u7b97\u4e00\u4e2a\u5e38\u91cf1&#xff08;\u4e00\u4e2a\u975eNULL\u503c&#xff09;&#xff0c;\u7136\u540e\u7edf\u8ba1\u7ed3\u679c\u96c6\u4e2d\u6709\u591a\u5c11\u4e2a1\u3002\u5b83\u4e5f\u4f1a\u5305\u542b\u503c\u4e3aNULL\u7684\u884c\u3002\u5728\u73b0\u4ee3MySQL&#xff08;\u7279\u522b\u662fInnoDB\u5f15\u64ce&#xff09;\u4e2d&#xff0c;\u4f18\u5316\u5668\u4f1a\u5c06count(1)\u548ccount(*)\u89c6\u4e3a\u5b8c\u5168\u76f8\u540c&#xff0c;\u6027\u80fd\u4e0a\u6ca1\u6709\u5dee\u522b\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0count(\u5217\u540d): \u7edf\u8ba1\u6307\u5b9a\u5217\u4e2d\u503c\u4e0d\u4e3aNULL\u7684\u884c\u7684\u6570\u91cf\u3002\u5b83\u4f1a\u5ffd\u7565\u503c\u4e3aNULL\u7684\u884c\u3002\u8fd9\u662f\u5b83\u4e0e\u524d\u4e24\u8005\u6700\u672c\u8d28\u7684\u529f\u80fd\u533a\u522b\u3002<\/p>\n<\/li>\n<\/ul>\n<h4>SQL \u793a\u4f8b<\/h4>\n<p>\u6211\u4eec\u521b\u5efa\u4e00\u5f20\u5b66\u751f\u7b7e\u5230\u8868&#xff0c;\u5176\u4e2d\u6709\u4e9b\u5b66\u751f\u8bf7\u5047\u4e86&#xff08;leave_reason\u00a0\u4e3a\u00a0NULL&#xff09;\u3002<\/p>\n<p>CREATE TABLE\u00a0student_checkin (<br \/>\n\u00a0 \u00a0 id\u00a0INTPRIMARY KEY\u00a0AUTO_INCREMENT,<br \/>\n\u00a0 \u00a0 student_name\u00a0VARCHAR(50),<br \/>\n\u00a0 \u00a0 checkin_time\u00a0TIMESTAMP,<br \/>\n\u00a0 \u00a0 leave_reason\u00a0VARCHAR(100)\u00a0&#8212; \u8bf7\u5047\u539f\u56e0&#xff0c;\u672a\u8bf7\u5047\u7684\u5b66\u751f\u6b64\u5217\u4e3aNULL<br \/>\n);<\/p>\n<p>INSERT INTO\u00a0student_checkin (student_name, checkin_time, leave_reason)\u00a0VALUES<br \/>\n(&#039;Alice&#039;, NOW(),\u00a0NULL),<br \/>\n(&#039;Bob&#039;, NOW(),\u00a0&#039;Sick Leave&#039;),<br \/>\n(&#039;Charlie&#039;, NOW(),\u00a0NULL),<br \/>\n(&#039;David&#039;, NOW(),\u00a0&#039;Personal Leave&#039;),<br \/>\n(&#039;Eve&#039;, NOW(),\u00a0NULL);<\/p>\n<p>&#8212; \u73b0\u5728\u6211\u4eec\u6765\u6267\u884c\u4e09\u79cd\u4e0d\u540c\u7684 COUNT \u67e5\u8be2<br \/>\nSELECT<br \/>\n\u00a0 \u00a0\u00a0COUNT(*)\u00a0AS\u00a0total_rows_star,<br \/>\n\u00a0 \u00a0\u00a0COUNT(1)\u00a0AS\u00a0total_rows_one,<br \/>\n\u00a0 \u00a0\u00a0COUNT(leave_reason)\u00a0AS\u00a0non_null_leave_reasons<br \/>\nFROM<br \/>\n\u00a0 \u00a0 student_checkin;<\/p>\n<p>\u67e5\u8be2\u7ed3\u679c:<\/p>\n<table>\n<tr>\n<td>\n<p>total_rows_star<\/p>\n<\/td>\n<td>\n<p>total_rows_one<\/p>\n<\/td>\n<td>\n<p>non_null_leave_reasons<\/p>\n<\/td>\n<\/tr>\n<tbody>\n<tr>\n<td>\n<p>5<\/p>\n<\/td>\n<td>\n<p>5<\/p>\n<\/td>\n<td>\n<p>2<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u7ed3\u679c\u89e3\u8bfb:<\/p>\n<ul>\n<li>\n<p>\u2022\u00a0COUNT(*)\u00a0\u548c\u00a0COUNT(1)\u00a0\u90fd\u8fd4\u56de\u4e86\u00a05&#xff0c;\u56e0\u4e3a\u5b83\u4eec\u7edf\u8ba1\u7684\u662f\u8868\u4e2d\u7684\u603b\u884c\u6570&#xff0c;\u4e0d\u7ba1\u4efb\u4f55\u5217\u7684\u503c\u662f\u4ec0\u4e48\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0COUNT(leave_reason)\u00a0\u8fd4\u56de\u4e86\u00a02&#xff0c;\u56e0\u4e3a\u5b83\u53ea\u7edf\u8ba1\u4e86\u00a0leave_reason\u00a0\u8fd9\u4e00\u5217\u503c\u4e0d\u4e3aNULL\u7684\u884c\u6570&#xff08;\u53ea\u6709Bob\u548cDavid\u8bf7\u5047\u4e86&#xff09;\u3002<\/p>\n<\/li>\n<\/ul>\n<hr \/>\n<h3>\u6545\u4e8b\u573a\u666f&#xff1a;\u73ed\u4e3b\u4efb\u7684\u4e09\u79cd\u70b9\u540d\u65b9\u5f0f<\/h3>\n<p>\u4f60\u662f\u4e00\u4f4d\u73ed\u4e3b\u4efb&#xff0c;\u9700\u8981\u7edf\u8ba1\u73ed\u7ea7&#xff08;\u6570\u636e\u8868&#xff09;\u7684\u51fa\u52e4\u60c5\u51b5\u3002<\/p>\n<h4>\u65b9\u5f0f\u4e00&#xff1a;COUNT(*)\u00a0\u2014 \u201c\u6328\u4e2a\u70b9\u4eba\u5934\u201d<\/h4>\n<p>\u8fd9\u662f\u6700\u76f4\u63a5\u3001\u6700\u539f\u59cb\u7684\u7edf\u8ba1\u65b9\u5f0f\u3002<\/p>\n<ul>\n<li>\n<p>\u2022\u00a0\u8001\u5e08\u7684\u64cd\u4f5c&#xff1a;<br \/>\n\u8001\u5e08\u7ad9\u5728\u8bb2\u53f0\u4e0a&#xff0c;\u60f3\u77e5\u9053\u201c\u4eca\u5929\u6559\u5ba4\u91cc\u4e00\u5171\u6709\u591a\u5c11\u4e2a\u5b66\u751f&#xff1f;\u201d\u3002\u4ed6\u4f38\u51fa\u624b\u6307&#xff0c;\u4ece\u7b2c\u4e00\u6392\u5f00\u59cb&#xff0c;\u6328\u4e2a\u6307\u5411\u6bcf\u4e00\u4e2a\u5b66\u751f&#xff08;\u6bcf\u4e00\u884c\u6570\u636e&#xff09;&#xff0c;\u5634\u91cc\u6570\u7740&#xff1a;\u201c1, 2, 3, 4, 5&#8230;\u201d\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0\u7279\u70b9&#xff1a;<br \/>\n\u8001\u5e08\u4e0d\u5173\u5fc3\u5b66\u751f\u53eb\u4ec0\u4e48&#xff0c;\u4e5f\u4e0d\u5173\u5fc3\u4ed6\u662f\u5426\u5728\u6253\u778c\u7761\u3002\u53ea\u8981\u8fd9\u4e2a\u5ea7\u4f4d\u4e0a\u6709\u4e00\u4e2a\u4eba&#xff0c;\u4ed6\u5c31\u4f1a\u88ab\u8ba1\u5165\u603b\u6570\u3002\u8fd9\u79cd\u65b9\u5f0f\u7edf\u8ba1\u7684\u662f\u7269\u7406\u5b58\u5728\u7684\u603b\u4eba\u6570\u3002<\/p>\n<\/li>\n<\/ul>\n<h4>\u65b9\u5f0f\u4e8c&#xff1a;COUNT(1)\u00a0\u2014 \u201c\u5212\u6b63\u5b57\u8ba1\u6570\u201d<\/h4>\n<p>\u8fd9\u662f\u4e00\u79cd\u770b\u8d77\u6765\u4e0d\u540c&#xff0c;\u4f46\u7ed3\u679c\u5b8c\u5168\u4e00\u6837\u7684\u65b9\u5f0f\u3002<\/p>\n<ul>\n<li>\n<p>\u2022\u00a0\u8001\u5e08\u7684\u64cd\u4f5c&#xff1a;<br \/>\n\u8fd9\u6b21\u8001\u5e08\u6362\u4e86\u4e00\u79cd\u65b9\u6cd5\u3002\u4ed6\u770b\u7740\u6559\u5ba4\u91cc\u7684\u5b66\u751f&#xff0c;\u6bcf\u770b\u5230\u4e00\u4e2a\u5b66\u751f&#xff0c;\u5c31\u5728\u9ed1\u677f\u4e0a\u5212\u4e00\u4e2a\u201c\u6b63\u201d\u5b57\u7684\u4e00\u7b14&#xff08;\u5e38\u91cf1&#xff09;\u3002\u6700\u540e&#xff0c;\u4ed6\u6570\u9ed1\u677f\u4e0a\u6709\u591a\u5c11\u7b14\u753b&#xff0c;\u5c31\u77e5\u9053\u603b\u4eba\u6570\u4e86\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0\u4e0eCOUNT(*)\u7684\u201c\u5386\u53f2\u6069\u6028\u201d&#xff1a;<br \/>\n\u5f88\u4e45\u4ee5\u524d&#xff0c;\u6709\u4e9b\u8001\u6559\u5e08\u8ba4\u4e3a\u201c\u6307\u4e00\u4e0b\u5b66\u751f\u5168\u8eab&#xff08;*&#xff09;\u201d\u8fd9\u4e2a\u52a8\u4f5c&#xff0c;\u6bd4\u5728\u9ed1\u677f\u4e0a\u201c\u7b80\u5355\u5212\u4e00\u7b14&#xff08;1&#xff09;\u201d\u8981\u6162\u3002\u4f46\u5728\u73b0\u4ee3\u5316\u7684\u201c\u667a\u6167\u6559\u5ba4\u201d&#xff08;\u73b0\u4ee3MySQL\u4f18\u5316\u5668&#xff09;\u91cc&#xff0c;\u7cfb\u7edf\u65e9\u5c31\u660e\u767d&#xff0c;\u8fd9\u4e24\u79cd\u65b9\u5f0f\u7684\u6838\u5fc3\u90fd\u662f\u201c\u770b\u4e00\u773c\u5b66\u751f\u201d&#xff0c;\u6240\u4ee5\u5b83\u4eec\u7684\u6548\u7387\u662f\u5b8c\u5168\u4e00\u6837\u7684\u3002COUNT(1)\u00a0\u548c\u00a0COUNT(*)\u00a0\u6027\u80fd\u6ca1\u6709\u533a\u522b&#xff0c;COUNT(*)\u00a0\u662fSQL\u6807\u51c6\u91cc\u66f4\u63a8\u8350\u7684\u5199\u6cd5\u3002<\/p>\n<\/li>\n<\/ul>\n<h4>\u65b9\u5f0f\u4e09&#xff1a;COUNT(\u5217\u540d)\u00a0\u2014 \u201c\u4ea4\u4e86\u4f5c\u4e1a\u7684\u8bf7\u4e3e\u624b&#xff01;\u201d<\/h4>\n<p>\u8fd9\u662f\u4e00\u79cd\u5e26\u6709\u7b5b\u9009\u6761\u4ef6\u7684\u7edf\u8ba1\u65b9\u5f0f\u3002<\/p>\n<ul>\n<li>\n<p>\u2022\u00a0\u8001\u5e08\u7684\u64cd\u4f5c&#xff1a;<br \/>\n\u4eca\u5929\u8001\u5e08\u7684\u76ee\u7684\u53d8\u4e86\u3002\u4ed6\u4e0d\u60f3\u77e5\u9053\u603b\u4eba\u6570&#xff0c;\u53ea\u60f3\u77e5\u9053\u201c\u4eca\u5929\u6709\u591a\u5c11\u4eba\u4ea4\u4e86\u4f5c\u4e1a&#xff1f;\u201d&#xff08;COUNT(homework_status)&#xff09;\u3002<br \/>\n\u4ed6\u671d\u53f0\u4e0b\u558a\u9053&#xff1a;\u201c\u6240\u6709\u4ea4\u4e86\u4f5c\u4e1a\u7684\u540c\u5b66&#xff0c;\u8bf7\u4e3e\u624b&#xff01;\u201d<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0\u7279\u70b9&#xff1a;<\/p>\n<ul>\n<li>\n<p>\u2022 \u90a3\u4e9b\u6ca1\u4ea4\u4f5c\u4e1a\u7684\u5b66\u751f&#xff08;homework_status\u00a0\u5b57\u6bb5\u4e3a\u00a0NULL&#xff09;&#xff0c;\u4f1a\u5fc3\u865a\u5730\u4f4e\u4e0b\u5934&#xff0c;\u7edd\u4e0d\u4f1a\u4e3e\u624b\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022 \u8001\u5e08\u6700\u7ec8\u7edf\u8ba1\u7684\u662f\u4e3e\u624b\u7684\u6570\u91cf\u3002<\/p>\n<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>\u2022\u00a0\u7ed3\u8bba&#xff1a;<br \/>\n\u8fd9\u79cd\u65b9\u5f0f\u7edf\u8ba1\u7684\u4e0d\u662f\u73ed\u7ea7\u7684\u603b\u4eba\u6570&#xff0c;\u800c\u662f**\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6&#xff08;\u6307\u5b9a\u5217\u7684\u503c\u4e0d\u4e3a\u7a7a&#xff09;**\u7684\u4eba\u6570\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>\u6545\u4e8b\u603b\u7ed3&#xff1a;<\/h3>\n<table>\n<tr>\n<td>\n<p>\u805a\u5408\u51fd\u6570<\/p>\n<\/td>\n<td>COUNT(*)\u00a0(\u70b9\u4eba\u5934)<\/td>\n<td>COUNT(1)\u00a0(\u5212\u6b63\u5b57)<\/td>\n<td>COUNT(\u5217\u540d)\u00a0(\u4e3e\u624b\u70b9\u540d)<\/td>\n<\/tr>\n<tbody>\n<tr>\n<td>\u7edf\u8ba1\u76ee\u6807<\/td>\n<td>\u603b\u884c\u6570<\/td>\n<td>\u603b\u884c\u6570<\/td>\n<td>\u6307\u5b9a\u5217\u4e2d\u975eNULL\u503c\u7684\u884c\u6570<\/td>\n<\/tr>\n<tr>\n<td>\u5904\u7406NULL<\/td>\n<td>\n<p>\u2705\u00a0\u8ba1\u7b97\u5728\u5185<\/p>\n<\/td>\n<td>\n<p>\u2705\u00a0\u8ba1\u7b97\u5728\u5185<\/p>\n<\/td>\n<td>\n<p>\u274c\u00a0\u5ffd\u7565<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\u6027\u80fd<\/td>\n<td>\u9ad8<\/p>\n<p>\u00a0(\u5b98\u65b9\u63a8\u8350)<\/p>\n<\/td>\n<td>\u9ad8<\/p>\n<p>\u00a0(\u4e0eCOUNT(*)\u76f8\u540c)<\/p>\n<\/td>\n<td>\u53ef\u80fd\u8f83\u4f4e<\/p>\n<p>\u00a0(\u9700\u989d\u5916\u5224\u65adNULL)<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\u6838\u5fc3\u6bd4\u55bb<\/td>\n<td>\u6328\u4e2a\u70b9\u540d&#xff0c;\u7edf\u8ba1\u603b\u4eba\u6570<\/td>\n<td>\u5212\u6b63\u5b57&#xff0c;\u7edf\u8ba1\u603b\u4eba\u6570<\/td>\n<td>\u4e3e\u624b\u70b9\u540d&#xff0c;\u7edf\u8ba1\u4ea4\u4f5c\u4e1a\u7684\u4eba\u6570<\/td>\n<\/tr>\n<tr>\n<td>\u4e00\u53e5\u8bdd\u603b\u7ed3<\/td>\n<td>\u6211\u6570\u7684\u662f\u201c\u884c\u201d\u3002<\/td>\n<td>\u6211\u548c\u697c\u4e0a\u4e00\u6837\u3002<\/td>\n<td>\u6211\u6570\u7684\u662f\u201c\u7279\u5b9a\u5217\u4e0d\u4e3a\u7a7a\u7684\u884c\u201d\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u6700\u7ec8\u5efa\u8bae&#xff1a;<\/p>\n<ul>\n<li>\n<p>\u2022 \u5f53\u4f60\u60f3\u7edf\u8ba1\u8868\u7684\u603b\u884c\u6570\u65f6&#xff0c;\u8bf7\u4f7f\u7528\u00a0COUNT(*)\u3002\u8fd9\u662f\u6700\u89c4\u8303\u3001\u6700\u6e05\u6670\u3001\u6027\u80fd\u4e5f\u6700\u597d\u7684\u9009\u62e9\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022 \u53ea\u6709\u5f53\u4f60\u7684\u9700\u6c42\u662f\u7edf\u8ba1\u67d0\u4e00\u5217\u4e2d\u6709\u6548\u503c&#xff08;\u975eNULL&#xff09;\u7684\u6570\u91cf\u65f6&#xff0c;\u624d\u4f7f\u7528\u00a0COUNT(\u5217\u540d)\u3002<\/p>\n<\/li>\n<li>\n<p>\u2022\u00a0COUNT(1)\u00a0\u53ea\u662f\u00a0COUNT(*)\u00a0\u7684\u4e00\u4e2a\u7b49\u4ef7\u5199\u6cd5&#xff0c;\u4e3a\u4e86\u4ee3\u7801\u7684\u6e05\u6670\u548c\u6807\u51c6\u5316&#xff0c;\u63a8\u8350\u4f7f\u7528COUNT(*)\u3002<\/p>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb280\u6b21\uff0c\u70b9\u8d5e10\u6b21\uff0c\u6536\u85cf4\u6b21\u3002\u2022 count(*): 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