sql - dateadd函数雪花中的变量

Question

我有一个这样的查询:

With cte as(
    Select min(date1) as min_date,
           max(date1) as max_date,
           id,
           city,
           time_id
   From some_table
   Group by id, city, time_id
),

range as
(select dateadd('month', row_number()over(order by null), (select min_date from cte)) as date_expand
From table(generator (row_count => 12*36))))

Select * from range;

它给出了这个错误: 单行子查询返回多行。

有没有办法在 dateadd 函数的第三个参数中传递变量？因为我的cte会根据group by子句返回很多min_date。 TIA

Answer 1

是的，SELECT 中的子选择只需要返回一行，您的 CTE 中有很多行。

如果你做了这样的事情，你的查询对我来说更有意义:

With some_table as (
    SELECT * FROM VALUES
        (1, 'new york', 10, '2020-01-01'::date),
        (1, 'new york', 10, '2020-02-01'::date),
        (2, 'christchurch', 20, '2021-01-01'::date)
    v(id, city, time_id, date1)
), cte as (
    Select 
       min(date1) as min_date,
       max(date1) as max_date,
       id,
       city,
       time_id
   FROM some_table
   GROUP BY 3,4,5
), range as (
    SELECT 
        id, city, time_id,
        dateadd('month', row_number()over(partition by id, city, time_id ORDER BY null), min_date) as date_expand
    FROM table(generator(rowcount =>12*36))
    CROSS JOIN cte
)
Select * from range;

但是如果你的 CTE 变成这样:

With cte as (
    Select 
       min(date1) as min_date,
       max(date1) as max_date
   FROM some_table
), range as (
    SELECT 
        dateadd('month', row_number()over(ORDER BY null), (select min_date from cte)) as date_expand
    FROM table(generator(rowcount =>2*4))
)
Select * from range;

这可行，因为只返回一个 min_date 值。

或者您可以找到最小的 min_dates，例如:

WITH cte as (
    Select 
       min(date1) as min_date,
       max(date1) as max_date,
       id,
       city,
       time_id
   FROM some_table
   GROUP BY 3,4,5
), range as (
    SELECT 
        dateadd('month', row_number()over(ORDER BY null), (select min(min_date) from cte)) as date_expand
    FROM table(generator(rowcount =>2*3))

)
Select * from range;