使用 `string_agg` 在 BigQuery SQL 中创建一个包含另一个连接的唯一元素的新列

Question

Given the following data:

WITH abc AS 
(
  SELECT 1234 id, 'Aug' month, 'P' value UNION ALL
  SELECT 1234, 'Sept', 'P' UNION ALL
  SELECT 4567, 'Sept', 'D' 
)
SELECT 
    month, 
    value, 
FROM abc

Which looks as:

I'd like to create a new column values which contains all values from the value columns.

So for this example data the new column would contain P, D .

Having done this the output would be (I've just written this out in Excel):

I tried to do this as follows:

WITH abc AS 
(
    SELECT 1234 id, 'Aug' month, 'P' value 
    UNION ALL
    SELECT 1234, 'Sept', 'P' 
    UNION ALL
    SELECT 4567, 'Sept', 'D' 
)
SELECT 
    month, 
    value, 
    STRING_AGG(distinct value, " & ") as str_agg
FROM abc

But I get this error:

SELECT list expression references column month which is neither grouped nor aggregated at [7:5]

I'm not sure how to aggregate/group the value column in order to satisfy this error.

Answer 1

Use below

select * 
from abc, (
  select string_agg(distinct value, ', ') values
  from abc
)

if applied to sample data in your question - output is