CS 112D Lecture Notes - DataSet Table Relations, Using DataSet Component (Chapter 5 part 2)

DataSet Table Relations and Foreign Key Constraints

• DataRelation - a class to store a parent/child relationship between two DataTables in a DataSet.
• The parent table is the one with the primary key, and the child table is the one with the foreign key. (e.g. Department is the parent of Employee.)
• DataRelation objects allow you to easily lookup related information in another table, using a DataSet.
• DataRelation objects are stored in the Relations collection of the DataSet. When constructing/adding them, specify the parent column followed by the child column.
• Example code can be seen in the btnCreateRelations_Click subroutine in the The DataSets solution from the text book
• When you add a DataRelation to a DataSet, two Constraint objects are automatically added as well: a ForeignKeyConstraint that enforces the referential integrity, and a UniqueConstraint that ensures that the parent table's primary key is unique.
• If a ForeignKeyConstraint is violated, a Data.InvalidConstraintException is thrown.

Using the DataSet Component

• Most of the things we've done with DataSets in code could be done using the DataSet Component from the Data tab of the Visual Studio Toolbox.

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