Supporting Master/detail Relationships
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You can create master/detail relationships between client datasets in your client application in the same way you set them up using any table-type dataset. For more information about setting up master/detail relationships in this way, see Creating Master/Detail Relationships.
However, this approach has two major drawbacks:
- The detail table must fetch and store all of its records from the application server even though it only uses one detail set at a time. (This problem can be mitigated by using parameters. For more information, see Limiting records with parameters.)
- It is very difficult to apply updates because client datasets apply updates at the dataset level and master/detail updates span multiple datasets. Even in a two-tiered environment, where you can use the database connection component to apply updates for multiple tables in a single transaction, applying updates in master/detail forms is tricky.
In multi-tiered applications, you can avoid these problems by using nested tables to represent the master/detail relationship. To do this when providing from datasets, set up a master/detail relationship between the datasets on the application server. Then set the DataSet property of your provider component to the master table. To use nested tables to represent master/detail relationships when providing from XML documents, use a transformation file that defines the nested detail sets.
When clients call the GetRecords method of the provider, it automatically includes the detail dataset as a DataSet field in the records of the data packet. When clients call the ApplyUpdates method of the provider, it automatically handles applying updates in the proper order.
- Creating Master-Detail Relationships
- Establishing Master-detail Relationships Using Parameters
- Managing Transactions in Multi-tiered Applications
- Extending the Interface of the Application Server
- Supporting State Information in Exposed Data Modules
- Setting Up the Data Module
- Using Multiple Server Data Modules