将 Table 加入自身以获得缺少日期的去年结果

Question

我有一个 table 的日期、频道和会话，我正在尝试使用连接命令为包含去年相关值的每一行添加列，但是，我想包括日期从去年开始，今年没有价值，反之亦然。问题是对于不存在的日期，我的行数加倍了。关于如何解决的任何想法？

SELECT
  ty.*,
  ly.Date as Date_LY,
  ly.Sessions as Sessions_LY
FROM
  `testjoin` AS ty
FULL JOIN
  `testjoin` as ly
  ON
  ly.Date = DATE_SUB(ty.Date, INTERVAl 1 YEAR)
  AND ly.Channel = ty.Channel

数据：

Date        Channel Sessions
01/01/2017  Email   5
02/02/2017  Email   10
01/01/2018  Email   11
02/02/2018  Email   17
01/01/2017  Organic 10
02/02/2017  Organic 15
01/01/2018  Organic 20

期望的输出：

Date    Channel Sessions    Sessions_LY
01/01/2017  Email   5   null
02/02/2017  Email   10  null
01/01/2018  Email   11  5
02/02/2018  Email   17  10
01/01/2017  Organic 10  null
02/02/2017  Organic 15  null
01/01/2018  Organic 20  10
02/02/2018  Organic null    15

实际输出：

Date        Channel Sessions    Sessions_LY
01/01/2017  Organic 10  
02/02/2017  Email   10  
02/02/2017  Organic 15  
01/01/2017  Email   5   
01/01/2018  Email   11  5
01/01/2018  Organic 20  10
02/02/2018  Email   17  10
                        15
                        11
                        20
                        17

Answer 1

我想你想要一个 cross join 来生成行和一个 left join 来引入值：

SELECT d.Date, c.Channel, ty.Sessions, ty_prev.Sessions
FROM (SELECT DISTINCT ty.Date
      FROM testjoin ty
     ) d CROSS JOIN
     (SELECT DISTINCT ty.channel FROM testjoin ty) c LEFT JOIN
     testjoin ty
     ON ty.Date = d.Date AND ty.Channel = c.Channel LEFT JOIN
     testjoin ty_prev
     ON ty_prev.Date = d.date - interval 1 year and ty.Channel = c.Channel;

Answer 2

根据需要使用 datepart

以 t（日期、频道、会话）为 ( select '01/01/2017', 'Email', 5 联合所有 select '02/02/2017', 'Email', 10 联合所有 select '01/01/2018', 'Email', 11 联合所有 select '02/02/2018', 'Email', 17 联合所有 select '01/01/2017', 'Organic', 10 联合所有 select '02/02/2017', 'Organic', 15 联合所有 select '01/01/2018', 'Organic', 20 ) select *, lag(sessions) over (partition by d.channel, datepart(mm, d.date) order by d.channel, datepart(mm, d.date))升来自 (select * 来自 ((SELECT DISTINCT t.Date 从 t) d 交叉连接 (SELECT DISTINCT t.channel FROM t) c)) d left join t on d.Date = t.Date and d.channel = t.channel 按 d.channel、datepart(yyyy,d.date)、datepart(mm, d.date)<br> 排序

Answer 3

您问题中的所有内容都表明您只有当前（2018 年）和之前（2017 年），因此以下内容基于此假设并且适用于 BigQuery 标准 SQL

#standardSQL
WITH temp AS (
  SELECT PARSE_DATE('%m/%d/%Y', Date) Date, Channel, Sessions
  FROM `project.dataset.your_table` 
), all_days AS ( 
  SELECT Date, Channel FROM temp UNION DISTINCT
  SELECT DATE_ADD(Date, INTERVAL 1 YEAR), Channel 
    FROM temp WHERE EXTRACT(YEAR FROM Date) = 2017
), all_data AS (
  SELECT Date, Channel, Sessions, FORMAT_DATE('%m%d', Date) day
  FROM all_days
  LEFT JOIN temp USING(Date, Channel)
)
SELECT Date, Channel, Sessions, 
  LAG(Sessions) OVER(PARTITION BY day, Channel ORDER BY Date) Sessions_LY
FROM all_data

您可以使用问题中的虚拟数据测试/玩上面的内容，如下所示

#standardSQL
WITH `project.dataset.your_table` AS (
  SELECT '01/01/2017' Date, 'Email' Channel, 5 Sessions UNION ALL
  SELECT '02/02/2017', 'Email', 10 UNION ALL
  SELECT '01/01/2018', 'Email', 11 UNION ALL
  SELECT '02/02/2018', 'Email', 17 UNION ALL
  SELECT '01/01/2017', 'Organic', 10 UNION ALL
  SELECT '02/02/2017', 'Organic', 15 UNION ALL
  SELECT '01/01/2018', 'Organic', 20 
), temp AS (
  SELECT PARSE_DATE('%m/%d/%Y', Date) Date, Channel, Sessions
  FROM `project.dataset.your_table` 
), all_days AS ( 
  SELECT Date, Channel FROM temp UNION DISTINCT
  SELECT DATE_ADD(Date, INTERVAL 1 YEAR), Channel 
    FROM temp WHERE EXTRACT(YEAR FROM Date) = 2017
), all_data AS (
  SELECT Date, Channel, Sessions, FORMAT_DATE('%m%d', Date) day
  FROM all_days
  LEFT JOIN temp USING(Date, Channel)
)
SELECT Date, Channel, Sessions, 
  LAG(Sessions) OVER(PARTITION BY day, Channel ORDER BY Date) Sessions_LY
FROM all_data
ORDER BY 2, 1

结果是

Row Date        Channel     Sessions    Sessions_LY  
1   2017-01-01  Email       5           null     
2   2017-02-02  Email       10          null     
3   2018-01-01  Email       11          5    
4   2018-02-02  Email       17          10   
5   2017-01-01  Organic     10          null     
6   2017-02-02  Organic     15          null     
7   2018-01-01  Organic     20          10   
8   2018-02-02  Organic     null        15

将 Table 加入自身以获得缺少日期的去年结果

Join Table to Itself for Last Year Results with Missing Dates

sql

join

google-bigquery

bigquery-standard-sql