Mysql select with IN, limit rows to 1 for each match - mysql

Question

lets say I have this table:
| id | record_id | date_updated |
|----|-----------|--------------|
| 1 | 1 | 19-03-2015 |
| 2 | 1 | 18-03-2015 |
| 3 | 1 | 17-03-2014 |
| 4 | 2 | 01-01-2015 |
| 5 | 2 | 05-02-2015 |
so the results I am looking for are :
| id | record_id | date_updated |
|----|-----------|--------------|
| 1 | 1 | 19-03-2015 |
| 4 | 2 | 01-01-2015 |
I have array with record ids.
$records = [1,2];
So I can do something like:
select * from `mytable`
WHERE `record_id` IN ($records)
AND mytable.date_update > 01-01-2014
AND mytable.date_updated < 12-12-2015
so mysql will select records wich match date_updated criteria ( and record id ofc ), which are more then 1 for each record ID, basically I want to make him limit the rows for each $record_id to 1
If it is even possible.
//it is super hard to explain the problem, the real case is that this is a sub query of another query, but the real example is 10 rows query and 100 columns table, so it will be even more hard to explain the situation and for someone to read it / udnerstands it. Hopefully someone will understand my problem, if not I will try to explain more.
Thanks

Answer 1

You can try using the group by clause
SELECT *
FROM `mytable`
WHERE id IN (
SELECT min(id)
FROM `mytable`
WHERE `record_id` IN ($records)
AND mytable.date_update > 01-01-2014
AND mytable.date_updated < 12-12-2015
group by record_id
);

Answer 2

There are many ways to get the record per group, and since you need only once you can easily do as below
select t1.* from table_name t1
where (
select count(*) from table_name t2
where t1.record_id = t2.record_id
) > =0
and
t1.date_updated > '2014-01-01' and date_updated < '2015-12-12'
group by t1.record_id ;
There are other way too using left join
select t1.* from table_name t1
left join table_name t2 on t1.record_id = t2.record_id
and t1.id >t2.id where t2.id is null
This will give you data with asc order with id
If you need data with max(id) for a record_id you can use
t1.id < t2.id
instead of
t1.id >t2.id
The same comparison you can do with first query.