Setting up a data relation

I'm new to C# and I'm trying to set up a data relation between a parent and child from an XML data source. I need to find a better explanation of how it is used. Any one know of a good web page or book for an explanation? Anyway, this is my specific question: My xml sheet (paraphrased) looks like this: ----------------------------- ABI/Inform Global 0 ... ... ------------------------------ The 'categories' table is a nested table and I want to be able to add and update the categories table in the dataset when the 'database' table is edited or updated. So I have to set up a relation: objRelation = New DataRelation("SOMENAMEHERE", objDataSet.Tables["database"].Columns["WHATGOESHERE?"], objDataSet.Tables["categories"].Columns["WHATGOESHERE?"]) So, this is my question: Based on the XML sheet above, what is supposed to go where it says "WHATGOESHERE?"? And why? I know, it's a beginner question, right, but I'm a beginner. -LJ

A relation between two tables is always a relation between a colum of each of the two tables. Every row of your "child" table, that has a value X in this column, is related to one or more rows of your "parent" table, that has the same value in this column. In your example, the parent table would be "database". It has the columns "name", "url", and "description". The child table "categories" has a column "art". But it also needs a column to connect is with the right row in the "database" table. It seems that the column "name" could be used for that connection. So these are your tables: [database] "name" "url" "description" [categories] "fk_name" "art" The column "fk_name" must now be related to "name": objDataSet.Relations.Add(new DataRelation("SomeRelation", objDataSet.Tables["database"].Columns["name"], objDataSet.Tables["categories"].Columns["fk_name"])); An exemplary entry in "databases" would look like this: name url description ---------------------------------------------------------- ABI/Inform Global http://an.url somedescription And the related rows in "categories would be: fk_name art ---------------------------- ABI/Inform Global 0 ABI/Inform Global 1 ABI/Inform Global 2 One important thing: to work correctly, the "name" column must only contain unique entries, no doubles. In most cases, it is better to create an integer column with auto-incrementing (and thus unique) values, and use these for relations.

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dak 022y ago
A relation between two tables is always a relation between a colum of each of the two tables. Every row of your "child" table, that has a value X in this column, is related to one or more rows of your "parent" table, that has the same value in this column. In your example, the parent table would be "database". It has the columns "name", "url", and "description". The child table "categories" has a column "art". But it also needs a column to connect is with the right row in the "database" table. It seems that the column "name" could be used for that connection. So these are your tables: [database] "name" "url" "description" [categories] "fk_name" "art" The column "fk_name" must now be related to "name": objDataSet.Relations.Add(new DataRelation("SomeRelation", objDataSet.Tables["database"].Columns["name"], objDataSet.Tables["categories"].Columns["fk_name"])); An exemplary entry in "databases" would look like this: name url description ---------------------------------------------------------- ABI/Inform Global http://an.url somedescription And the related rows in "categories would be: fk_name art ---------------------------- ABI/Inform Global 0 ABI/Inform Global 1 ABI/Inform Global 2 One important thing: to work correctly, the "name" column must only contain unique entries, no doubles. In most cases, it is better to create an integer column with auto-incrementing (and thus unique) values, and use these for relations.