如何根据相似的 id 将同一列中的值合并到一个新列中

Question

So right now, I have a table, baseoil, that includes a description column, a substring column that has parsed data from the description column, and a ID column. I want to combine the parsed values from the substring into a new column based on the the ID of the row while also keeping the data that does not have a duplicate ID. For example:

Description          |Substring  |ID     |
---------------------|-----------|-------|                     
100 GALLONS OF SN5484|100 GALLONS|8330780|
---------------------|-----------|-------|
100 GALLONS OF SN5484|SN5484     |8330780|
---------------------|-----------|-------|
25 LITERS OF TY50000 |TY50000    |7545215|

I want the new row to look like this:

Description          |Substring  |ID     |Combined          |
---------------------|-----------|-------|------------------|                     
100 GALLONS OF SN5484|100 GALLONS|8330780|100 GALLONS SN5484|
---------------------|-----------|-------|------------------|
100 GALLONS OF SN5484|SN5484     |8330780|100 GALLONS SN5484|
---------------------|-----------|-------|------------------|
25 LITERS OF TY50000 |TY50000    |7545215|TY50000           |

How would I go about doing this?

Answer 1

One option is to join the table with an aggregate query that computes the combined substring s for each id :

select b.*, c.combined
from baseoil b
inner join (select id, string_agg(substring, ' ') combined from baseoil group by id) c 
    on b.id = c.id

Demo on DB Fiddle :

description           | substring   |      id | combined          
:-------------------- | :---------- | ------: | :-----------------
100 GALLONS OF SN5484 | 100 GALLONS | 8330780 | 100 GALLONS SN5484
100 GALLONS OF SN5484 | SN5484      | 8330780 | 100 GALLONS SN5484
25 LITERS OF TY50000  | TY50000     | 7545215 | TY50000

Answer 2

Use string_agg() as a window function:

select bo.*,
       string_agg(substring order by ?, ' ') over (partition by id) as combined
from baseoil bo;

The ? is for the column that specifies the ordering. Otherwise, the substrings may be combined in any arbitrary ordering.