How can this SQL query be improved? - sql

Question

This code actually works, but I guess it can be done in an easier way, or even more efficient (because I guess comparing strings like that is not a problem but may be). I tried to convert everything into datetime and not string but failed.
This code takes the date and time row from one table, CONCATing them and compares it to the datetime row from another table. The result is: 2019-12-02 09:00:00
It is just a regular Date, Time and Datetime parameters in the table. Like this Date 2019-11-17, Time 09:00:00, Datetime 2019-01-15 16:00:00
SELECT
MAX(CONCAT(f_ini, CONCAT( " ", h_ini)))
FROM posible_work
WHERE
fk_id_asigned = 100573 AND
(SELECT MAX(CONCAT(f_ini, CONCAT( " ", h_ini)))
FROM posible_work) >
(SELECT MAX(RIGHT(f_fin,19)) AS FechaAVI FROM next_work WHERE fk_id_worker = 100573)

Answer 1

Apart from the fact that you force concat() to be called twice when you can use it with 3 arguments (or more), one additional problem would be this condition:
(SELECT MAX(CONCAT(f_ini, CONCAT( " ", h_ini)))
FROM posible_work) >
(SELECT MAX(RIGHT(f_fin,19)) AS FechaAVI FROM next_work WHERE fk_id_worker = 100573)
Why not use in the left side of the inequality just concat(...) and you repeat SELECT...MAX(..)...?
I don't think that this breaks your code's logic:
SELECT
MAX(CONCAT(f_ini, ' ', h_ini))
FROM posible_work
WHERE
fk_id_asigned = 100573
AND
CONCAT(f_ini, ' ', h_ini) >
(SELECT MAX(RIGHT(f_fin,19)) AS FechaAVI FROM next_work WHERE fk_id_worker = 100573)
Also it could be better if you did not hardcode 100573 twice.
Just use aliases properly:
SELECT
MAX(CONCAT(p.f_ini, ' ', p.h_ini))
FROM posible_work p
WHERE
p.fk_id_asigned = 100573
AND
CONCAT(p.f_ini, ' ', p.h_ini) >
(SELECT MAX(RIGHT(f_fin,19)) AS FechaAVI FROM next_work WHERE fk_id_worker = p.fk_id_asigned)