SQL选择一个表中的所有列和另一个表上另一列的最大值

Question

This is my first question in stackoverflow and I hope I get an answer soon to my problem. :) I tried searching for quite some time from other sources but unfortunately, couldn't find a working answer.

So, I am working on a project and since I am a newbie to sql, I cannot do this:

I have 2 tables:

"Customers" with columns "id", "name", "last name" ("id" is primary key)
"Sessions" with columns "id", "Customer", "entrydate" ("id" is primary key)

"Customer" from "Sessions" is tied to "id" from "Customers". (foreign key)

I need a query that returns all columns from table "Customers" with one additional column showing the entrydate of the latest "Sessions" record, of each Customer of course. "Sessions" table may have many records for an individual "Customers" record, as you can imagine.

Thanks everybody in advance and hope to get an answer soon.

Answer 1

I may be missing something really obvious but this sounds really really basic sql the kind you'd find in a sql tutorial https://www.w3schools.com/SQL/sql_groupby.asp

SELECT C.name,c.lastName,MAX(S.entryDate) FROM customers C
inner join Sessions S ON S.CustomerId=C.Id
group by C.name,C.lastName

Answer 2

就这么简单。

SELECT C.id,C.name,c.lastName,MAX(S.entryDate) as lastEntry FROM customers C join Sessions S ON S.CustomerId=C.Id group by C.id