How do I specify a 1 to many relationship?

I want to specify a relationship between two data tables in a dataset.
(Both data tables come from executing stored procedures in SQL Server.)
When I tried to add the relationship through the Relations property of the
dataset, I got the following error message:



"The columns don't currently have unique values."



I believe the problem is there is a one-to-many relationship between the
parent data table and the child data table. So my question is how do I
specify that when I create the relationship? Is there a property of the
DataColumn object that I have to specify? Right now I'm trying to link the
two by common columns (client number and case number); should I specify some
other column in the child's DataColumn which would be unique for each
client/case? (I didn't do this in this case, because the example I saw in
David Sceppa's book "Microsoft ADO.NET" didn't do this. I had thought that
I had to specify only those columns from both data tables which would be
linked between the parent and child DataColumns.)



I am using ADO.NET 1.1.





Rod

W
Wed Oct 26 18:30:17 CDT 2005

Comments inline
"Rod" <rodf@newsgroups.nospam> wrote in message
news:eyHwhpn2FHA.3912@TK2MSFTNGP15.phx.gbl...
>I want to specify a relationship between two data tables in a dataset.
>(Both data tables come from executing stored procedures in SQL Server.)
>When I tried to add the relationship through the Relations property of the
>dataset, I got the following error message:
>
>
>
> "The columns don't currently have unique values."
>
>
>
> I believe the problem is there is a one-to-many relationship between the
> parent data table and the child data table. So my question is how do I
> specify that when I create the relationship?
--Do you have a Key set up on the tables and/or unique constraints?
(http://www.knowdotnet.com/articles/datarelation.html)
Is there a property of the
> DataColumn object that I have to specify? Right now I'm trying to link
> the two by common columns (client number and case number); should I
> specify some other column in the child's DataColumn which would be unique
> for each client/case? (I didn't do this in this case, because the example
> I saw in David Sceppa's book "Microsoft ADO.NET" didn't do this. I had
> thought that I had to specify only those columns from both data tables
> which would be linked between the parent and child DataColumns.)
The PrimaryKey property of the table takes an Array of DataColumns [even if
there's only one column - you have to use an Array which can be a little
confusing
>
>
>
> I am using ADO.NET 1.1.
>
>
>
>
>
> Rod
>
>

Cor
Thu Oct 27 04:35:21 CDT 2005

Rod,

Especially for your question I have made what I think is the most minimized
sample to show a datarelation in a dataset.

http://www.vb-tips.com/default.aspx?ID=d667d78f-4b08-42ef-ba3b-8b8620d93761

I hope this helps,

Cor

Rod
Thu Oct 27 09:25:09 CDT 2005

Thank you, Cor, I'll give it a look.

Rod


"Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message
news:eVAVknt2FHA.2600@tk2msftngp13.phx.gbl...
> Rod,
>
> Especially for your question I have made what I think is the most
> minimized sample to show a datarelation in a dataset.
>
> http://www.vb-tips.com/default.aspx?ID=d667d78f-4b08-42ef-ba3b-8b8620d93761
>
> I hope this helps,
>
> Cor
>

Rod
Thu Oct 27 09:56:12 CDT 2005

Cor,

I went to your VB-Tips website and saw what you've done. I added a third
column from my child table to the relationship, which would really be
appropriate for this situation. So, now I have an array of DataColumns for
the parent with client number and case number in it, and I have an array of
DataColumns for the child with client number, case number and sequence
number. When I run my program I now get an error message which says:

"ParentColumns and ChildColumns should be the same length."

Well, they can't be, if I'm going to have a one-to-many parent-child
relationship. Even your example on the website you gave did not have the
ParentColumns and ChildColumns having the same length.

So, what's missing now?

Rod


"Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message
news:eVAVknt2FHA.2600@tk2msftngp13.phx.gbl...
> Rod,
>
> Especially for your question I have made what I think is the most
> minimized sample to show a datarelation in a dataset.
>
> http://www.vb-tips.com/default.aspx?ID=d667d78f-4b08-42ef-ba3b-8b8620d93761
>
> I hope this helps,
>
> Cor
>

Cor
Thu Oct 27 12:01:36 CDT 2005

Rod,

I did forgot, the messages tells in my opinion that your parent table has
columns (relation) which are not unique and therefore a one to many cannot
be made.

>>The columns don't currently have unique values."

Sorry

Cor

JAW
Fri Oct 28 10:08:02 CDT 2005

I believe what the message is telling you is that the two columns must be of the same data type and size, i.e. they both
must be a number 5 or a character 10, etc.

Rod wrote:
> Cor,
>
> I went to your VB-Tips website and saw what you've done. I added a third
> column from my child table to the relationship, which would really be
> appropriate for this situation. So, now I have an array of DataColumns for
> the parent with client number and case number in it, and I have an array of
> DataColumns for the child with client number, case number and sequence
> number. When I run my program I now get an error message which says:
>
> "ParentColumns and ChildColumns should be the same length."
>
> Well, they can't be, if I'm going to have a one-to-many parent-child
> relationship. Even your example on the website you gave did not have the
> ParentColumns and ChildColumns having the same length.
>
> So, what's missing now?
>
> Rod
>
>
> "Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message
> news:eVAVknt2FHA.2600@tk2msftngp13.phx.gbl...
>
>>Rod,
>>
>>Especially for your question I have made what I think is the most
>>minimized sample to show a datarelation in a dataset.
>>
>>http://www.vb-tips.com/default.aspx?ID=d667d78f-4b08-42ef-ba3b-8b8620d93761
>>
>>I hope this helps,
>>
>>Cor
>>
>
>
>