Re: Lookup columns

> Hi
>
> I know this is not a direct firebird .net provider related question but I 
> didn't get an answer on the M$ newsgroups so will try here to, sorry. :)
>
> Is there a way to create lookup columns in tables in the typed datasets?
>
> Like
>
> CityTable
> ----------
> CityID
> CityName
>
> Employee
> --------
> EmployeeID
> EmployeeName
> City -> foreign key to CityTable.CityID
> CityName -> lookup column, will get the value from CityTable according the 
> City value

> First the CityTable records are loaded and then the Employee. I could do 
> this with SQL but that means I would load the same data 2 times and I'm 
> trying to lower the network usage as the lines that we are using are slow.
>
> In expression column I was trying to use the Parent keyword but with no 
> luck. So is there a way to do this?
well, you can do it by hand, it's pretty fast

employeeTable.BeginLoadData();
foreach (TypedDataSet.EmployeeRow employee in employeeTable.Rows) {
 employee.CityName = employee.CityRow.Name;
}
employee.EndLoadData();


you can speed this up further by going throught the dataset designer and 
skip all the casting
that are along. and if you're going to loads further records (if you batch 
loads instead of loading full tables), you can put a employeeTable.Select 
instead of Rows

The other solution is to make many-to-many relation and put another table 
in-between that way you'll have the children relationships it require 
(although I am fairly sertain it should work with parent)

the third is to use LinQ (it is on the microsoft lab page, still in beta, 
designed for C# 3.0, but it allow full blown relational queries)

> Thx
>
> Zoltan
HTH
CUIN Kaczy

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