按日分组：select DATE_FORMAT(o.OrderDate,'%Y%m%d') weeks,count(*) count from orders o group by weeks;
按月分组：select DATE_FORMAT(o.OrderDate,'%Y%m') weeks,count(*) count from orders o group by weeks;
按周分组： select DATE_FORMAT(o.OrderDate,'%Y_%u') weeks,count(*) count from orders o group by weeks;
按季度分组：select CONCAT(YEAR(o.OrderDate),'_',quarter(o.OrderDate)) qu,count(*) count from orders o group by qu;
每个人都需要一台速度更快、更稳定的 PC。随着时间的推移，垃圾文件、旧注册表数据和不必要的后台进程会占用资源并降低性能。幸运的是，许多工具可以让 Windows 保持平稳运行。
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