https://blog.youkuaiyun.com/qq_37644539zh-cnhttps://blog.youkuaiyun.com/https://blog.youkuaiyun.com/qq_37644539/article/details/163138020https://blog.youkuaiyun.com/qq_37644539/article/details/163138020qq_37644539Thu, 23 Jul 2026 17:22:41 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/163134197https://blog.youkuaiyun.com/qq_37644539/article/details/163134197qq_37644539Thu, 23 Jul 2026 16:42:12 +0800)会得到NULL之外的数据行数。只有SELECT子句和HAVING子句（以及ORDER BY子句）中能够使用聚合函数。ORDER BY子句中可以使用列的编号（在ORDER BY子句中不要使用列编号）聚合函数会将NULL排除在外。使用GROUP BY子句时，SELECT子句中不能出现聚合键之外的列名。想要计算值的种类时，可以在COUNT函数的参数中使用DISTINCT。SELECT子句中未包含的列也可以在ORDER BY子句中使用。]]>https://blog.youkuaiyun.com/qq_37644539/article/details/162912817https://blog.youkuaiyun.com/qq_37644539/article/details/162912817qq_37644539Wed, 15 Jul 2026 21:57:12 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/162911688https://blog.youkuaiyun.com/qq_37644539/article/details/162911688qq_37644539Wed, 15 Jul 2026 20:05:33 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/99424919https://blog.youkuaiyun.com/qq_37644539/article/details/99424919qq_37644539Tue, 13 Aug 2019 13:18:44 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/97664631https://blog.youkuaiyun.com/qq_37644539/article/details/97664631qq_37644539Mon, 12 Aug 2019 14:44:33 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/97668846https://blog.youkuaiyun.com/qq_37644539/article/details/97668846qq_37644539Mon, 12 Aug 2019 14:44:08 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/97892162https://blog.youkuaiyun.com/qq_37644539/article/details/97892162qq_37644539Mon, 12 Aug 2019 14:43:35 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/97888400https://blog.youkuaiyun.com/qq_37644539/article/details/97888400qq_37644539Mon, 12 Aug 2019 14:43:10 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/93376664https://blog.youkuaiyun.com/qq_37644539/article/details/93376664qq_37644539Sat, 22 Jun 2019 23:35:17 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/90757190https://blog.youkuaiyun.com/qq_37644539/article/details/90757190qq_37644539Mon, 03 Jun 2019 19:04:52 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/90747478https://blog.youkuaiyun.com/qq_37644539/article/details/90747478qq_37644539Mon, 03 Jun 2019 09:55:43 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/90740780https://blog.youkuaiyun.com/qq_37644539/article/details/90740780qq_37644539Sun, 02 Jun 2019 16:54:29 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/90739912https://blog.youkuaiyun.com/qq_37644539/article/details/90739912qq_37644539Sun, 02 Jun 2019 15:51:25 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89890637https://blog.youkuaiyun.com/qq_37644539/article/details/89890637qq_37644539Mon, 06 May 2019 20:25:06 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89715434https://blog.youkuaiyun.com/qq_37644539/article/details/89715434qq_37644539Tue, 30 Apr 2019 20:38:29 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89578792https://blog.youkuaiyun.com/qq_37644539/article/details/89578792qq_37644539Fri, 26 Apr 2019 23:59:25 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89578053https://blog.youkuaiyun.com/qq_37644539/article/details/89578053qq_37644539Fri, 26 Apr 2019 22:42:13 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89216273https://blog.youkuaiyun.com/qq_37644539/article/details/89216273qq_37644539Thu, 11 Apr 2019 17:38:05 +0800https://blog.youkuaiyun.com/qq_37644539/article/details/89213533https://blog.youkuaiyun.com/qq_37644539/article/details/89213533qq_37644539Thu, 11 Apr 2019 16:16:22 +0800