无法在 Redshift 上将 JOIN 与generate_series 一起使用

Question

当在简单的 select 语句中使用时，Redshift 上的generate_series 函数按预期工作。

WITH series AS (
    SELECT n as id from generate_series (-10, 0, 1) n
) SELECT * FROM series;
-- Works fine

一旦我添加 JOIN 条件，redshift 就会抛出

com.amazon.support.exceptions.ErrorException：函数 generate_series（整数，整数，整数）“不支持”

DROP TABLE testing;
CREATE TABLE testing (
  id INT
);
WITH series AS (
  SELECT n as id from generate_series (-10, 0, 1) n
) SELECT * FROM series S JOIN testing T ON S.id = T.id;
-- Function "generate_series(integer,integer,integer)" not supported.

红移版本

SELECT version();
-- PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.1485

是否有任何解决方法可以使这项工作正常进行？

Answer 1

generate_series

。它只能在领导节点上独立工作。

解决方法是对任何具有足够行数的表使用

row_number

：

with 
series as (
    select (row_number() over ())-11 from some_table limit 10
) ...

此外，这个问题已经被问过多次了

Answer 2

您是对的，这在 Redshift 上不起作用。 请参阅

此处。

最简单的解决方法是预先使用该表中的值“手动”创建一个永久表，例如您可以在该表上包含 -1000 到 +1000 的行，然后从该表中选择范围，

所以对于你的例子，你会有类似的东西

WITH series AS (
  SELECT n as id from (select num as n from newtable where num between -10 and 0) n
) SELECT * FROM series S JOIN testing T ON S.id = T.id;

这对你有用吗？

或者，如果您无法事先创建表格或不想这样做，您可以使用类似的东西

with ten_numbers as (select 1 as num union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9 union select 0)
,generted_numbers AS
(
    SELECT (1000*t1.num) + (100*t2.num) + (10*t3.num) + t4.num-5000 as gen_num
    FROM ten_numbers AS t1
      JOIN ten_numbers AS t2 ON 1 = 1
      JOIN ten_numbers AS t3 ON 1 = 1
      JOIN ten_numbers AS t4 ON 1 = 1
)
select  gen_num from generted_numbers
where gen_num between -10 and 0
order by 1;

Answer 3

使用 redshift 生成行的正确方法是使用WITH RECURSIVE CTE，如下所示：

with recursive t(n) as (
  select 0::integer
  union all
  select n+1 from t where n <= 100
)
select n*2 as two_times_n from t;

您可以与任何您想要的真实桌子连接。

请参阅

https://docs.aws.amazon.com/redshift/latest/dg/r_WITH_clause.html