WHERE和HAVING可以互相替换，效果相同

WHERE在数据分组前对行进行过滤，HAVING在数据分组后对组进行过滤

如果查询中同时有WHERE和HAVING，HAVING会先执行

WHERE子句中可以使用聚合函数，HAVING子句中不能使用聚合函数

HAVING SUM(金额) > 1000

WHERE 订单日期 >= DATE_SUB(CURDATE(), INTERVAL 30 DAY)

ORDER BY 总金额 DESC

GROUP BY 客户ID

计算每日新用户在7天后的活跃比例

统计每个用户在首次活跃后第7天是否活跃

确定每个用户的首次活跃日期

统计每个日期的新用户数

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT

FROM → ON → JOIN → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT

FROM → WHERE → SELECT → GROUP BY → HAVING → ORDER BY → LIMIT

SELECT → FROM → WHERE → GROUP BY → HAVING → ORDER BY → LIMIT

使用窗口函数：MIN(active_date) OVER(PARTITION BY user_id)

使用自连接：通过user_id自关联找到最小日期

使用FIRST_VALUE：FIRST_VALUE(active_date) OVER(PARTITION BY user_id ORDER BY active_date)

使用FIRST_VALUE：FIRST_VALUE(active_date) OVER(PARTITION BY user_id ORDER BY active_date)

HAVING COUNT(DISTINCT order_id) >= 2

HAVING COUNT(order_id) >= 2

HAVING COUNT(user_id) >= 2

以上都可以，但A最简单直接