{"id":5914,"date":"2024-11-14T10:52:48","date_gmt":"2024-11-14T02:52:48","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5914\/"},"modified":"2024-11-14T10:52:48","modified_gmt":"2024-11-14T02:52:48","slug":"sql%e6%80%8e%e4%b9%88%e6%8f%90%e5%8f%96count%e7%9a%84%e7%bb%93%e6%9e%9c","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5914\/","title":{"rendered":"sql\u600e\u4e48\u63d0\u53d6count\u7684\u7ed3\u679c"},"content":{"rendered":"<blockquote><p>\n  \u5728 sql \u4e2d\uff0c\u901a\u8fc7\u4f7f\u7528 count() \u51fd\u6570\u53ef\u63d0\u53d6\u67e5\u8be2\u7ed3\u679c\u7684\u8bb0\u5f55\u6570\u3002\u65b9\u6cd5\u5305\u62ec\uff1a\u4f7f\u7528 select \u8bed\u53e5\u9009\u62e9 count() \u7ed3\u679c\u3002\u7ed9\u7ed3\u679c\u8d77\u522b\u540d\uff0c\u4ee5\u4fbf\u540e\u7eed\u5f15\u7528\u3002\u4f7f\u7528 group by \u5b50\u53e5\u5206\u7ec4\u5e76\u8ba1\u7b97\u6bcf\u4e2a\u7ec4\u7684 count()\u3002\u4f7f\u7528 having \u5b50\u53e5\u8fc7\u6ee4\u5206\u7ec4\u540e\u7684 count() \u7ed3\u679c\u3002\u5c06 count() \u7ed3\u679c\u4f5c\u4e3a\u5b50\u67e5\u8be2\u7684\u4e00\u90e8\u5206\u63d0\u53d6\u3002\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202406\/03\/2024060322183632522.jpg\" class=\"aligncenter\" title=\"sql\u600e\u4e48\u63d0\u53d6count\u7684\u7ed3\u679c\u63d2\u56fe\" alt=\"sql\u600e\u4e48\u63d0\u53d6count\u7684\u7ed3\u679c\u63d2\u56fe\" \/><\/p>\n<p><strong>\u5982\u4f55\u4ece SQL \u67e5\u8be2\u4e2d\u63d0\u53d6 COUNT \u7ed3\u679c<\/strong><\/p>\n<p>\u5728 SQL \u4e2d\uff0cCOUNT() \u51fd\u6570\u7528\u4e8e\u8ba1\u7b97\u7279\u5b9a\u5217\u6216\u6761\u4ef6\u4e2d\u7684\u8bb0\u5f55\u6570\u3002\u4e3a\u4e86\u63d0\u53d6 COUNT() \u7ed3\u679c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\uff1a<\/p>\n<p><strong>1. \u4f7f\u7528 SELECT \u8bed\u53e5<\/strong><\/p>\n<p>\u6700\u76f4\u63a5\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 SELECT \u8bed\u53e5\u4ece COUNT() \u51fd\u6570\u4e2d\u9009\u62e9\u7ed3\u679c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre>SELECT COUNT(*)\nFROM table_name;<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u8fd9\u5c06\u8fd4\u56de\u8868\u4e2d\u6240\u6709\u8bb0\u5f55\u7684\u8ba1\u6570\u3002<\/p>\n<p><strong>2. \u4f7f\u7528 AS \u5173\u952e\u5b57\u7ed9\u7ed3\u679c\u522b\u540d<\/strong><\/p>\n<p>\u53ef\u4ee5\u7ed9 COUNT() \u51fd\u6570\u7684\u7ed3\u679c\u4e00\u4e2a\u522b\u540d\uff0c\u4ee5\u4fbf\u5728\u540e\u7eed\u67e5\u8be2\u4e2d\u5f15\u7528\u3002\u4f8b\u5982\uff1a<\/p>\n<pre>SELECT COUNT(*) AS record_count\nFROM table_name;<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u8fd9\u5c06\u521b\u5efa\u540d\u4e3a &#8220;record_count&#8221; \u7684\u522b\u540d\uff0c\u53ef\u4ee5\u7528\u4e8e\u5176\u4ed6\u67e5\u8be2\u6216\u64cd\u4f5c\u3002<\/p>\n<p><strong>3. \u4f7f\u7528 GROUP BY \u5b50\u53e5<\/strong><\/p>\n<p>GROUP BY \u5b50\u53e5\u53ef\u7528\u4e8e\u5c06\u6570\u636e\u5206\u7ec4\u5e76\u5728\u6bcf\u4e2a\u7ec4\u4e2d\u8ba1\u7b97 COUNT()\u3002\u4f8b\u5982\uff1a<\/p>\n<pre>SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department;<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u8fd9\u5c06\u8fd4\u56de\u5305\u542b\u6bcf\u4e2a\u90e8\u95e8\u53ca\u5176\u5458\u5de5\u6570\u7684\u8868\u3002<\/p>\n<p><strong>4. \u4f7f\u7528 HAVING \u5b50\u53e5<\/strong><\/p>\n<p>HAVING \u5b50\u53e5\u53ef\u7528\u4e8e\u5728 COUNT() \u7ed3\u679c\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6\u65f6\u8fc7\u6ee4\u5206\u7ec4\u6570\u636e\u3002\u4f8b\u5982\uff1a<\/p>\n<pre>SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department\nHAVING COUNT(*) &gt; 10;<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u8fd9\u5c06\u8fd4\u56de\u5458\u5de5\u6570\u5927\u4e8e 10 \u7684\u6240\u6709\u90e8\u95e8\u3002<\/p>\n<p><strong>5. \u4f7f\u7528\u5b50\u67e5\u8be2<\/strong><\/p>\n<p>COUNT() \u7ed3\u679c\u4e5f\u53ef\u4ee5\u4f5c\u4e3a\u5b50\u67e5\u8be2\u7684\u4e00\u90e8\u5206\u63d0\u53d6\u3002\u4f8b\u5982\uff1a<\/p>\n<pre>SELECT *\nFROM table_name\nWHERE id IN (SELECT id FROM table_name ORDER BY COUNT(*) DESC LIMIT 10);<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u8fd9\u5c06\u4ece &#8220;table_name&#8221; \u8868\u4e2d\u9009\u62e9\u8bb0\u5f55\u6570\u6700\u591a\u7684\u524d 10 \u6761\u8bb0\u5f55\u3002<\/p>\n<p>\u4ee5\u4e0a\u5c31\u662fsql\u600e\u4e48\u63d0\u53d6count\u7684\u7ed3\u679c\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>\u5728 sql \u4e2d\uff0c\u901a\u8fc7\u4f7f\u7528 count() \u51fd\u6570\u53ef\u63d0\u53d6\u67e5\u8be2\u7ed3\u679c\u7684\u8bb0\u5f55\u6570\u3002\u65b9\u6cd5\u5305\u62ec\uff1a\u4f7f\u7528 select \u8bed\u53e5\u9009\u62e9 count() \u7ed3\u679c\u3002\u7ed9\u7ed3\u679c\u8d77\u522b\u540d\uff0c\u4ee5\u4fbf\u540e\u7eed\u5f15\u7528\u3002\u4f7f\u7528 group by \u5b50\u53e5\u5206\u7ec4\u5e76\u8ba1\u7b97\u6bcf\u4e2a\u7ec4\u7684 count()\u3002\u4f7f\u7528 having \u5b50\u53e5\u8fc7\u6ee4\u5206\u7ec4\u540e\u7684 count() \u7ed3\u679c\u3002\u5c06 count() \u7ed3\u679c\u4f5c\u4e3a\u5b50\u67e5\u8be2\u7684\u4e00\u90e8\u5206\u63d0\u53d6\u3002 \u5982\u4f55\u4ece SQL \u67e5\u8be2\u4e2d\u63d0\u53d6 COUNT \u7ed3\u679c \u5728 SQL \u4e2d\uff0cCOUNT() \u51fd\u6570\u7528\u4e8e\u8ba1\u7b97\u7279\u5b9a\u5217\u6216\u6761\u4ef6\u4e2d\u7684\u8bb0\u5f55\u6570\u3002\u4e3a\u4e86\u63d0\u53d6 COUNT() \u7ed3\u679c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\uff1a 1. \u4f7f\u7528 SELECT \u8bed\u53e5 \u6700\u76f4\u63a5\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 SELECT \u8bed\u53e5\u4ece COUNT() \u51fd\u6570\u4e2d\u9009\u62e9\u7ed3\u679c\u3002\u4f8b\u5982\uff1a SELECT COUNT(*) FROM table_name; \u767b\u5f55\u540e\u590d\u5236 \u8fd9\u5c06\u8fd4\u56de\u8868\u4e2d\u6240\u6709\u8bb0\u5f55\u7684\u8ba1\u6570\u3002 2. \u4f7f\u7528 AS \u5173\u952e\u5b57\u7ed9\u7ed3\u679c\u522b\u540d \u53ef\u4ee5\u7ed9 COUNT() \u51fd\u6570\u7684\u7ed3\u679c\u4e00\u4e2a\u522b\u540d\uff0c\u4ee5\u4fbf\u5728\u540e\u7eed\u67e5\u8be2\u4e2d\u5f15\u7528\u3002\u4f8b\u5982\uff1a SELECT COUNT(*) AS [&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-5914","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5914","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=5914"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5914\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5914"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5914"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5914"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}