Question

create table #customer (
id int not null primary key,
cust_name varchar(12),
oldid int null
)

insert into #customer values(1,'XYZ',null) 
insert into #customer values(2,'XYZ',1) 
insert into #customer values(3,'XYZ',2) 
insert into #customer values(4,'ABC',null) 
insert into #customer values(5,'ABC',4) 
insert into #customer values(6,'DEF',null) 
insert into #customer values(7,'DEF',6) 
insert into #customer values(8,'DEF',7) 
insert into #customer values(9,'DEF',8) 


select * from #customer
-- output

id          cust_name    oldid
----------- ------------ -----------
1           XYZ          NULL
2           XYZ          1
3           XYZ          2
4           ABC          NULL
5           ABC          4
6           DEF          NULL
7           DEF          6
8           DEF          7
9           DEF          8

This is a simulation when a record is renewed, the new record stores the id of its older record. The chain continues and goes down to the very first record created for that customer.

What I want is I issue a command like

select * from #customer where id=3

This should put not only the record with id=3 but all its old version, that is records 2 and 1 also.

select * from #customer id=4

should pull only that record (oldid = null)

---

Enhancement (optional): If someone issue a commond

select * from #customer where id=8

I would somehow like to indicate, a new record exist for this customer. How can I do that? Assume I am going to use in ASP.NET application.

Answer 1

Can get all of the older records for a given Customer using a CTE. Something like

DECLARE @CustomerId int
SET @CustomerId = 8

;
WITH Records (Id, Cust_name, OldId) AS (
    SELECT * FROM #Customer
    WHERE Id = @CustomerId
    UNION ALL
    SELECT C.* FROM Records R
        INNER JOIN #Customer C on C.Id = R.OldId)
SELECT * FROM Records

You have options for indicating whether a newer record exists, you may want to include newer record(s) in the result set or just a bit flag, but in any case the query would be like

SELECT * FROM #Customer WHERE OldId = @CustomerId