通过与id链接的另一个表的另一个属性连接表

Question

Edit : I did a mistake the Invoices Table carry the transactionId

I have 3 tables :

Transactions  Reconciliations             Invoices
id            num    line transId         id   Code    transId
--            ---   ---- -------          --   ----    -------------
3              1    1    3                5   Code 5   3
6              1    2    6                9   Code 9   8    
7              1    3    7                12  Code 12  11
8              2    1    8
12             2    2    12
10             3    1    10
11             3    2    11 

and this Query :

select
    t1.id   -- transaction id
    t2.num  -- reconciliation number
    t3.Code -- Invoice code
from Transactions t1
left outer join Reconciliations t2 on t2.transId = t1.id
left outer join Invoices t3 on t3.transId = t1.id

Giving the following result :

id      num     code
--     ---     ----
3       1       Code 5
6       1       null
7       1       null
8       2       Code 9
12      2       null
10      3       null
11      3       Code 12

But what I want is this :

id      num     code
--      ---     ----
3       1       Code 5
6       1       Code 5
7       1       Code 5
8       2       Code 9
12      2       Code 9
10      3       Code 12
11      3       Code 12

To put words on it when the linked Invoice table gives null I want to join on all the records from Reconciliations with the same Reconciliation number.

Edit : I would like the Code in invoices to be shared across all transactions that shares the same Reconciliation number

I have tried to do thru outer apply and sub query but I cannot figure out a way to achieve it. Have you any idea ?

Answer 1

You seem to want to spread the InvoiceId in Transactions up to the next value.

Here is one method:

select t.*
       (select top 1 InvoiceId
        from Transactions t2
        where t2.id <= t.id and t2.InvoiceId is not NULL
        order by id desc
       ) as newInvoiceId
from transactions t;

You can then substitute this into your query:

select
    t1.id   -- transaction id
    t2.num  -- reconciliation number
    t3.Code -- Invoice code
from (select t.*
            (select top 1 InvoiceId
             from Transactions t2
             where t2.id <= t.id and t2.InvoiceId is not NULL
             order by id desc
            ) as newInvoiceId
     from transactions t
    ) t1
left outer join Reconciliations t2 on t2.transid = t1.id
left outer join Invoices t3 on t3.id = t1.transid ;

Answer 2

The solution is to join to Reconciliations again before joining to Invoices :

select t.id, r.num, i.Code
from Transactions t
join Reconciliations r on r.transId = t.id
join Reconciliations r2 on r2.num = r.num
join Invoices i on i.transId = r2.transId

Note that the joins are now inner joins ( requiring a match), and how you easily make the connection to the right Invoice via the shared Reconciliation.num value - using inner joins means you only get the invoice row that matches.

To see this query in action, execute it on SQLFiddle

---

Edit: To cater for missing invoices

Use left join to invoices, but you need a group by with max() to limit the joins to just one invoice per transaction (without the max() you get lots of extra rows with null Code):

select t.id, r.num, max(i.Code) as Code
from Transactions t
join Reconciliations r on r.transId = t.id
join Reconciliations r2 on r2.num = r.num
left join Invoices i on i.transId = r2.transId
group by t.id, r.num

To see this query in action, where I have invalidated invoice 12 from above fiddle, execute it on SQLFiddle