Question

My database consists of 2 tables. Im using MySQL.

Table 1

cars = id(int,PRIMARYKEY), reg(int), type(int)

Table 2

jobs = ref(int,PRIMARYKEY), id (int), date(date)

I need a SELECT statement which would get me all the cars which have not had a job in the past 3 weeks.

(i.e: If a car has not had a job in the past 3 weeks, then that car(id) would be returned.)

I know there would be several ways to do this however I am not up to speed in sql yet :<

Answer 1

This is a good use case for NOT EXISTS:

select c.id,c.reg,c.type
from cars c
where not exists 
(
  select NULL
  from jobs j
  where j.id = c.id
  and j.date >= CURRENT_DATE - INTERVAL 3 WEEK
);