Question

Please advise on how to merge two results in to one using SQL Server 2005.

I have the situation where an Account can have up to two Settlement Instructions and this has been modeled like so:

The slim-ed down schema:

Account
---------------------
Id
AccountName
PrimarySettlementId (nullable)
AlternateSettlementId (nullable)


SettlementInstruction
----------------------
Id
Name

The output I want is a single result set with a select statement something along the lines of this which will allow me to construct some java objects in my Spring row mapper:

select
  Account.Id as accountId, 
  Account.AccountName as accountName, 

  s1.Id as primarySettlementId, 
  s1.Name as primarySettlementName, 

  s2.Id as alternateSettlementId, 
  s2.Name as alternateSettlementName

I’ve tried various things but cannot find a way to get the result set merged in to one where the primary and alternate FK’s are not null.

Finally I have searched the forum, but nothing quite seems to fit with what I need.

Answer 1

You need an outer join.

select
  Account.Id as accountId, 
  Account.AccountName as accountName, 

  s1.Id as primarySettlementId, 
  s1.Name as primarySettlementName, 

  s2.Id as alternateSettlementId, 
  s2.Name as alternateSettlementName
from Account
     left join SettlementInstruction s1 ON s1.Id = Account.PrimarySettlementId
     left join SettlementInstruction s2 ON s2.Id = Account.SecondarySettlementId
where /* ... */