How to merge these queries and create a single query

I have these three working queries:

SELECT a, time, b, c 
FROM table_first 
WHERE created_at >= timestamp '2022-02-13 00:00:00' 
  AND a = 'LK0601' 
ORDER BY time DESC
LIMIT 1;

SELECT a, time, b, c 
FROM table_first 
WHERE created_at >= timestamp '2022-02-13 00:00:00' 
  AND a = 'DT9834'
ORDER BY time DESC
LIMIT 1;

SELECT a, time, b, c 
FROM table_first 
WHERE created_at >= timestamp '2022-02-13 00:00:00' 
  AND a = 'LM3526' 
ORDER BY time DESC
LIMIT 1;

In these queries, I get the latest entry for the different values of a.

How can I merge them into one query?

So that it becomes something like the following:

SELECT a, time, b, c 
FROM table_first 
WHERE created_at >= timestamp '2022-02-13 00:00:00' 
  AND a IN ('LM3526','DT9834','LK0601') 
GROUP BY a 
ORDER BY time DESC
LIMIT 1;

From the above query, I want to get the latest rows for all the different values of a.

I am using the PostgreSQL database.

>Solution :

You may use DISTINCT ON here:

SELECT DISTINCT ON (a) a, time, b, c
FROM table_first
WHERE created_at >= timestamp '2022-02-13 00:00:00' AND
      a IN ('LK0601', 'DT9834', 'LM3526')
ORDER BY a, time DESC;