Limiting rows from a joined table I have 2 tables Part and PartDtl.  PartDtl contains one row for each order that has been placed for that part. 

PartNum | Description | ...
1234    | 1234 desc   | ...
2345    | 2345 desc   | ...

PartNum | Qty | DueDate     | ...
1234    | 12  | 2015/11/15  | ...
1234    | 66  | 2015/11/17  | ...
1234    | 45  | 2015/11/18  | ...
1234    | 33  | 2015/11/16  | ...
2345    | 77  | 2015/11/12  | ...
2345    | 43  | 2016/01/01  | ...


I use the follwing sql to get the data:

select 
  p.PartNum, 
  pd.Quantity,
  pd.DueDate
from 
  Erp.Part as p, 
  Erp.PartDtl pd
where
  p.Company = pd.Company and 
  p.PartNum = pd.PartNum and 
  pd.StockTrans = 'TRUE'
order by 1, 3, 2


The problem is that some parts have lots of orders placed and I only need to see the first few.  For example:

PartNum | Qty | DueDate     
1234    | 12  | 2015/11/15  
1234    | 33  | 2015/11/16  
1234    | 66  | 2015/11/17  
2345    | 77  | 2015/11/12  
2345    | 43  | 2016/01/01  


I haven't been able to figure out how to have the first 3 orders due of each part.

I have tried a sub-query, but haven't figured out the syntax.

Can you show me the way, please.

nb - there are other fields which are shown in the sql which I don't think are relevent to this query.  I'm using a recent MS SQL-Server database.
This should work:

SELECT      *
FROM        (SELECT         ROW_NUMBER() OVER (PARTITION BY p.Partnum 
                                               ORDER BY     p.Partnum
                                                            , pd.DueDate
                                                            , pd.Quantity) AS rownumber
                            , p.Partnum
                            , pd.Quantity
                            , pd.DueDate
                FROM        Part       AS p
                INNER JOIN  PartDtl    AS pd
                    ON      p.Company  = pd.Company
                        AND p.PartNum  = pd.PartNum
            ) AS sub
WHERE       sub.rownumber &lt;= 3
ORDER BY    sub.Partnum
            , sub.DueDate
            , sub.Quantity


You were using old SQL syntax, I converted the old join type to an INNER JOIN.
Also changed the numbers in the ORDER BY clause, as this might cause problems when you change the order of your selected columns.