Combining between two tables in MySQL and getting the distinct answer - mysql

Question

I know this has probably been asked before but I am trying to find the correct way to this and I have been struggling for the past week or so.
So we have two sets of data for example, one table is called 'Order Log' and another is called 'Customer Information'
and here are example of the two data set
NOTE: The order log will sometimes have order from the same customer twice
Order Log Table
Customer ID
Date
Order Number
Order Amount
sgcwi
2022-06-11
124
3
gbtfc
2022-07-09
12
4
crownwood
2022-04-08
123
1
kcsi
2022-02-24
543
1
ulsteri
2022-08-08
423
2
gbtfc
2022-07-08
1254
3
ulsteri
2022-04-08
345
2
kcsi
2022-07-13
64
1
crownwood
2022-07-04
55
1
Customer Information Table
Customer Name
Customer ID
Contact
Sagen Private
sgcwi
email
Granten Viel
gbtfc
phone
Crownwood LTD
crownwood
email
Kings College
kcsi
email
Ulster FC
ulsteri
phone
So what my question is, how do i write an sql query that gives me back the the last order for each customer from the Order Log table withhin a span of the last 6 Months and returns me back the customer name for each of those selected data from the customer Informationt table. like such
The Sql Query Return that i want
Customer Name
Customer ID
Date
Sagen Private
sgcwi
2022-06-11
Granten Viel
gbtfc
2022-06-11
Crownwood LTD
crownwood
2022-07-04
Kings College
kcsi
2022-07-13
Ulster FC
ulsteri
2022-08-08
so far I have figured out to get the result from the Log table that I gave to use the query
"SELECT DISTINCT orderLog.customerID FROM Order WHERE qslogv2.date >= DATE_ADD(NOW(), INTERVAL -3 MONTH);
But I am yet to figure out how do i connect the Customer Information table to this query so it returns me the appropriate customer name along with the query.
I tried using the above query that I mentioned and also tried the UNION keyword in MySQL but to my demise I was not able to get to a point where I got that desired result.

Answer 1

Use JOIN-statement combined with MAX + GROUP BY.
In JOIN you tell what columns match in the joined tables. In your case it is the Customer ID.
With GROUP BY, you divide the rows into sets (based on the customer) and then applies the MAX-function for each of those sets, so that you will get the latest date for each customer.
select
c.name,
c.id,
max(ol.date)
from customerInformation c
join orderLog ol on ol.customerID=c.id
where ol.date between date_sub(now(), interval 6 month) and now()
group by c.name, c.id