sql 查詢至少連續n天下單的用戶

下圖為一張訂單表（order1），現希望查找出至少連續3天下單的用戶。

第一步：將訂單表按UserId分組根據日期Date排序

第二步：用日期Date減去對應的排序號Num，若日期是連續的，則相減的結果Datedif相等。

第三步：按UserId，Datedif分組計數，得到各用戶的連續下單天數。

第四步：篩選連續下單天數≥n的用戶

# 訂單表  order1
# UserId  Date  Orders
# step1: 將訂單表按UserId分組根據日期Date排序
 SELECT UserId,`Date`,orders,
 row_number() over(PARTITION BY UserId ORDER BY DATE)Num
 FROM order1
 # step2: 用日期Date減去對應的排序號Num，若日期是連續的，則相減的結果Datedif相等。
 SELECT UserId,`Date`,`Date`-Num  AS DateDif
 FROM 
 (
 SELECT UserId,`Date`,orders,
 row_number() over(PARTITION BY UserId ORDER BY DATE)Num
 FROM order1
 )a
 # step3:按UserId，Datedif分組計數，得到各用戶的連續下單天數。
 SELECT UserId,COUNT(1) AS Consecutive
 FROM (
  SELECT UserId,`Date`,`Date`-Num  AS DateDif
 FROM 
 (
 SELECT UserId,`Date`,orders,
 row_number() over(PARTITION BY UserId ORDER BY DATE)Num
 FROM order1
 )a
 )b
 GROUP BY UserId,DateDif
 # 篩選連續下單天數≥3的用戶
 SELECT Userid
 FROM
 (
 SELECT UserId,COUNT(1) AS Consecutive
 FROM (
 SELECT UserId,`Date`,`Date`-Num  AS DateDif
 FROM 
 (
 SELECT UserId,`Date`,orders,
 row_number() over(PARTITION BY UserId ORDER BY DATE)Num
 FROM order1
 )a
 )b
 GROUP BY UserId,DateDif
 )c
 WHERE Consecutive>=3