{"id":159977,"date":"2024-11-03T19:15:21","date_gmt":"2024-11-03T11:15:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/159977\/"},"modified":"2024-11-03T19:15:23","modified_gmt":"2024-11-03T11:15:23","slug":"mssql-%e6%95%99%e7%a8%8b-sql-count-%e5%87%bd%e6%95%b8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/159977\/","title":{"rendered":"MSSQL \u6559\u7a0b SQL COUNT() \u51fd\u6578"},"content":{"rendered":"<h1 id=\"mssql-%e6%95%99%e7%a8%8b-sql-count-%e5%87%bd%e6%95%b8-cIbgzYDNRH\">MSSQL \u6559\u7a0b SQL COUNT() \u51fd\u6578<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u4e2d\uff0cSQL COUNT() \u51fd\u6578\u662f\u4e00\u500b\u975e\u5e38\u91cd\u8981\u7684\u5de5\u5177\uff0c\u7279\u5225\u662f\u5728\u4f7f\u7528 Microsoft SQL Server (MSSQL) \u6642\u3002\u9019\u500b\u51fd\u6578\u7684\u4e3b\u8981\u529f\u80fd\u662f\u8a08\u7b97\u8cc7\u6599\u8868\u4e2d\u7b26\u5408\u7279\u5b9a\u689d\u4ef6\u7684\u884c\u6578\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e SQL COUNT() \u51fd\u6578\u7684\u7528\u6cd5\u3001\u7bc4\u4f8b\u4ee5\u53ca\u6700\u4f73\u5be6\u8e10\u3002<\/p>\n<h2 id=\"count-%e5%87%bd%e6%95%b8%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-cIbgzYDNRH\">COUNT() \u51fd\u6578\u7684\u57fa\u672c\u8a9e\u6cd5<\/h2>\n<p>SQL COUNT() \u51fd\u6578\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT COUNT(column_name) FROM table_name WHERE condition;<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>column_name<\/code> \u662f\u4f60\u60f3\u8981\u8a08\u7b97\u7684\u5217\u540d\uff0c<code>table_name<\/code> \u662f\u8cc7\u6599\u8868\u7684\u540d\u7a31\uff0c\u800c <code>condition<\/code> \u5247\u662f\u53ef\u9078\u7684\u689d\u4ef6\uff0c\u7528\u65bc\u904e\u6ffe\u8a08\u7b97\u7684\u884c\u3002<\/p>\n<h2 id=\"count-%e5%87%bd%e6%95%b8%e7%9a%84%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-cIbgzYDNRH\">COUNT() \u51fd\u6578\u7684\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<h3 id=\"1-%e8%a8%88%e7%ae%97%e6%89%80%e6%9c%89%e8%a1%8c%e6%95%b8-cIbgzYDNRH\">1. \u8a08\u7b97\u6240\u6709\u884c\u6578<\/h3>\n<p>\u5982\u679c\u4f60\u60f3\u8981\u8a08\u7b97\u8cc7\u6599\u8868\u4e2d\u6240\u6709\u7684\u884c\u6578\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT COUNT(*) FROM Employees;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de <code>Employees<\/code> \u8cc7\u6599\u8868\u4e2d\u7684\u7e3d\u884c\u6578\u3002<\/p>\n<h3 id=\"2-%e8%a8%88%e7%ae%97%e7%89%b9%e5%ae%9a%e5%88%97%e7%9a%84%e8%a1%8c%e6%95%b8-cIbgzYDNRH\">2. \u8a08\u7b97\u7279\u5b9a\u5217\u7684\u884c\u6578<\/h3>\n<p>\u5982\u679c\u4f60\u53ea\u60f3\u8a08\u7b97\u67d0\u4e00\u5217\u4e2d\u975e\u7a7a\u503c\u7684\u884c\u6578\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT COUNT(FirstName) FROM Employees;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de <code>FirstName<\/code> \u5217\u4e2d\u975e\u7a7a\u503c\u7684\u6578\u91cf\u3002<\/p>\n<h3 id=\"3-%e4%bd%bf%e7%94%a8-where-%e5%ad%90%e5%8f%a5%e9%80%b2%e8%a1%8c%e6%a2%9d%e4%bb%b6%e8%a8%88%e7%ae%97-cIbgzYDNRH\">3. \u4f7f\u7528 WHERE \u5b50\u53e5\u9032\u884c\u689d\u4ef6\u8a08\u7b97<\/h3>\n<p>\u4f60\u4e5f\u53ef\u4ee5\u4f7f\u7528 <code>WHERE<\/code> \u5b50\u53e5\u4f86\u8a08\u7b97\u7b26\u5408\u7279\u5b9a\u689d\u4ef6\u7684\u884c\u6578\u3002\u4f8b\u5982\uff0c\u8a08\u7b97\u6240\u6709\u5728\u67d0\u500b\u90e8\u9580\u5de5\u4f5c\u7684\u54e1\u5de5\u6578\u91cf\uff1a<\/p>\n<pre><code>SELECT COUNT(*) FROM Employees WHERE Department = 'Sales';<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u5728 <code>Sales<\/code> \u90e8\u9580\u5de5\u4f5c\u7684\u54e1\u5de5\u6578\u91cf\u3002<\/p>\n<h2 id=\"count-%e5%87%bd%e6%95%b8%e7%9a%84%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-cIbgzYDNRH\">COUNT() \u51fd\u6578\u7684\u6ce8\u610f\u4e8b\u9805<\/h2>\n<ul>\n<li><strong>NULL \u503c\u7684\u8655\u7406\uff1a<\/strong>\u4f7f\u7528 <code>COUNT(column_name)<\/code> \u6642\uff0cNULL \u503c\u4e0d\u6703\u88ab\u8a08\u7b97\u5728\u5167\uff1b\u800c\u4f7f\u7528 <code>COUNT(*)<\/code> \u6642\uff0c\u6240\u6709\u884c\u90fd\u6703\u88ab\u8a08\u7b97\u3002<\/li>\n<li><strong>\u6027\u80fd\u8003\u91cf\uff1a<\/strong>\u5728\u5927\u578b\u8cc7\u6599\u8868\u4e2d\uff0c\u4f7f\u7528 COUNT() \u51fd\u6578\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u6027\u80fd\uff0c\u7279\u5225\u662f\u7576\u6c92\u6709\u9069\u7576\u7684\u7d22\u5f15\u6642\u3002<\/li>\n<li><strong>\u8207 GROUP BY \u7d50\u5408\uff1a<\/strong>COUNT() \u51fd\u6578\u5e38\u8207 <code>GROUP BY<\/code> \u5b50\u53e5\u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u4fbf\u5c0d\u5206\u7d44\u7684\u6578\u64da\u9032\u884c\u8a08\u7b97\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e5%90%88-group-by-%e7%9a%84%e7%af%84%e4%be%8b-cIbgzYDNRH\">\u7d50\u5408 GROUP BY \u7684\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528 <code>GROUP BY<\/code> \u7684\u7bc4\u4f8b\uff0c\u8a08\u7b97\u6bcf\u500b\u90e8\u9580\u7684\u54e1\u5de5\u6578\u91cf\uff1a<\/p>\n<pre><code>SELECT Department, COUNT(*) AS EmployeeCount\nFROM Employees\nGROUP BY Department;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b\u90e8\u9580\u53ca\u5176\u5c0d\u61c9\u7684\u54e1\u5de5\u6578\u91cf\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-cIbgzYDNRH\">\u7e3d\u7d50<\/h2>\n<p>SQL COUNT() \u51fd\u6578\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u5feb\u901f\u7372\u53d6\u8cc7\u6599\u8868\u4e2d\u7684\u884c\u6578\u3002\u7121\u8ad6\u662f\u8a08\u7b97\u6240\u6709\u884c\u3001\u7279\u5b9a\u5217\u7684\u975e\u7a7a\u503c\uff0c\u9084\u662f\u7d50\u5408\u689d\u4ef6\u9032\u884c\u8a08\u7b97\uff0cCOUNT() \u51fd\u6578\u90fd\u80fd\u63d0\u4f9b\u6709\u6548\u7684\u89e3\u6c7a\u65b9\u6848\u3002\u4e86\u89e3\u5176\u7528\u6cd5\u548c\u6700\u4f73\u5be6\u8e10\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u8cc7\u6599\u5eab\u67e5\u8a62\u7684\u6548\u7387\u548c\u6e96\u78ba\u6027\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u8cc7\u6599\u5eab\u7ba1\u7406\u6216\u5176\u4ed6\u6280\u8853\u554f\u984c\u6709\u8208\u8da3\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4e86\u89e3\u66f4\u591a\u8cc7\u8a0a\uff0c\u7279\u5225\u662f\u6211\u5011\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u65b9\u6848\uff0c\u63d0\u4f9b\u7a69\u5b9a\u7684\u96f2\u4f3a\u670d\u5668\u89e3\u6c7a\u65b9\u6848\uff0c\u52a9\u60a8\u8f15\u9b06\u7ba1\u7406\u8cc7\u6599\u5eab\u548c\u61c9\u7528\u7a0b\u5f0f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2 MSSQL \u6559\u7a0b\u4e2d\u7684 SQL COUNT() \u51fd\u6578\uff0c\u638c\u63e1\u5982\u4f55\u8a08\u7b97\u8cc7\u6599\u884c\u6578\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6548\u7387\u8207\u6e96\u78ba\u6027\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-159977","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/159977","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=159977"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/159977\/revisions"}],"predecessor-version":[{"id":159978,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/159977\/revisions\/159978"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=159977"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=159977"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=159977"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}