Prevent Duplicate Job Card Number

Question

Hi, I am using the below SBO code which tries to block users inputting duplicate job card number when issuing items from after sales warehouses, but it doesn't seem to be working.
6)Block Duplicate Job Card No's in After Sales Deliveries
IF @transaction_type IN (N'A', N'U') AND (@Object_type = N'60')
Begin
IF  EXISTS(SELECT T0.DocEntry FROM dbo.[@SBO_SP_NOTIFICATION] T0 where IsNull(T0.U_Active,'')in('Yes') and T0.U_QueryNo = 'GI012') 
BEGIN
IF EXISTS (SELECT T0.DocEntry FROM [dbo].[IGE1] T0, dbo.[OIGE] T1 WHERE T1.U_DocType = 'After Sales Delivery' AND T1.DocEntry = T0.DocEntry   AND  T1.DOCENTRY= @list_of_cols_val_tab_del)
BEGIN
declare  @JCNo int
set @JCNo=-1
set @JCNo=(SELECT T0.LineNum+1 FROM IGE1 T0
WHERE T0.DocEntry =@list_of_cols_val_tab_del
and exists(select linenum from IGE1
          where WhsCode in ('NAWW_KE','MASW_KE') and BlockNum=T0.BlockNum
               and DocEntry<T0.DocEntry) )
If @JCNo<>-1
begin
SET @error = 10
SET @error_message = N'SBO: GI012-Duplicate Job card No '
end
end
END
END
Please help.

Answer 1

Thanks,
It now works after I added unique constraints to each of the fields.
Google results showed me that ORA-00001 is Oracle's Duplicate message and I added a condition in the SQLException Catch area and it catches all my Duplicate entry attempts and shows message to the user.
Here is what I have and would like to know if this is an efficient way I am doing this??
try
// db stuff
catch (SQLException sqle)
    String message = sqle.getMessage();  
    if (message.indexOf("ORA-00001") != -1)
        out.println("Duplicate Data entry.");  
    else
      out.println("some other ORA error");  
}