PostgreSQL search lists of substrings in string column

I have the following table in a postreSQL database (simplified for clarity):

  | serverdate |           name | value 
  |-------------------------------------
0 | 2019-12-01 | A LOC 123 DISP | 1
1 | 2019-12-01 | B LOC 456 DISP | 2
2 | 2019-12-01 | C LOC 777 DISP | 0
3 | 2019-12-01 | D LOC 000 DISP | 10
4 | 2019-12-01 | A LOC 700 DISP | 123
5 | 2019-12-01 | F LOC 777 DISP | 8

name columns is of type string. The substrings LOC and DISP can have other values of different lengths but are not of interest in this question.

The problem: I want to SELECT the rows that only contain a certain substring. There are several substrings, passed as an ARRAY, in the following format:

['A_123', 'F_777'] # this is an example only

I would want to select all the rows that contain the first part of the substring (sepparating it by the underscore ‘_’), as well as the second. In this example, with the mentioned array, I should obtain rows 0 and 5 (as these are the only ones with exact matches in both parts of the):

  | serverdate |           name | value 
  |-------------------------------------
0 | 2019-12-01 | A LOC 123 DISP | 1
5 | 2019-12-01 | F LOC 777 DISP | 8

Row 4 has the first part of the substring correct, but not the other one, so it shouldn’t be returned. Same thing with row 2 (only second part matches).

How could this query be done? I’m relatively new to SQL.

This query is part of process in Python, so I can adjust the input parameter (the substring array) if needed, but the behaviour must be the same as the one described.

Thanks!

Answer

Have you tried with regexp_replace and a subquery?

SELECT * FROM 
  (SELECT serverdate, substring(name from 1 for 1)||'_'||
          regexp_replace(name, 'D*', '', 'g') AS name, value 
  FROM t) j 
WHERE name IN('A_123', 'F_777');

Or using a CTE

WITH j AS (
SELECT serverdate, substring(name from 1 for 1)||'_'||
       regexp_replace(name, 'D*', '', 'g') AS name2, 
       value,name
FROM t 
) SELECT serverdate,name,value FROM j 
  WHERE name2 IN('A_123', 'F_777');


 serverdate |      name      | value 
------------+----------------+-------
 2019-12-01 | A LOC 123 DISP |     1
 2019-12-01 | F LOC 777 DISP |     8
(2 Zeilen)

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Answer