从另一个表返回单个记录，每个事务具有多个记录

Question

How can I create a query that will return the latest Soa LoanableAmount based on the LoanApplicationDate.

Ex: For LoanID = 1, I want to get the Soa record with SoaID = 2 since this is the latest loanable amount for this LoanApplicationDate - 2017-07-01.

So far this is what I have accomplished:

select * 
  from Loan L
  join Soa S
    ON S.EmployeeID = L.EmployeeID
where S.TransactionDate <= L.LoanApplicationDate

To illustrate what I want to accomplish, please see screenshot below.

https://www.db-fiddle.com/f/3PBossUJLYQTQZJfZymiph/0

Answer 1

I think you need to set the condition on the join:

select  
  L.LoanID,
  L.EmployeeID,
  L.LoanAmount,
  L.LoanApplicationDate,
  S.LoanableAmount,
  S.TransactionDate
from Loan L join Soa S
ON S.EmployeeID = L.EmployeeID and
S.TransactionDate = (select max(TransactionDate) from Soa where TransactionDate <= L.LoanApplicationDate)

See the demo

Answer 2

SQL DEMO

select * 
from Loan L
join Soa S
  ON S.EmployeeID = L.EmployeeID 
 and S.TransactionDate = 
        (select max(S2.TransactionDate) 
         from Soa S2
         where S2.TransactionDate <= L.LoanApplicationDate
           and S2.`EmployeeID` = L.`EmployeeID`
        )

Answer 3

I think you want a join and then to filter to get the most recent date:

select l.*, s.*
from Loan l join
     Soa s 
     on s.employeeid = l.employeeid
where s.TransactionDate <= (select max(s2.TransactionDate)
                       from Soa s2
                       where s2.employeeid = l.employeeid and
                             s2.TransactionDate <= l.LoanApplicationDate 
                      );

Answer 4

The below query will give you all employee ids with loanable amount withdrawn on latest date

     Select employee_id, 
       LoanableAmount 
      transactionDate from table 
     having
  transactionDate=max(transactionDate)
    group by employee_id

Answer 5

You need to run a subquery for each row:

select q.*, S.LoanableAmount, S.TransactionDate from
   (select  
     L.*
     ,(select SoaID from Soa  x where x.EmployeeID = L.EmployeeID and x.TransactionDate <= L.LoanApplicationDate order by TransactionDate DESC limit 1) as SoaID 
   from Loan L) q
join Soa S on S.SoaID = q.SoaID

Line 4 will give you the SoaID of the row in the Soa table that has the newest date that is less than or equal to the Application Date, then with that ID you just join and show the rest of the fields.