作用:返回匹配指定条件的行数。博智达直线电机平台
语法:SELECT COUNT(*) FROM table_name
//计算客户 "Carter" 的订单数 SELECT COUNT(Customer) AS CustomerNilsen FROM Orders WHERE Customer='Carter';
posted on 2019-11-21 14:32 佰草伐 阅读(309) 评论(0) 编辑 收藏 举报
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