vrijdag 9 oktober 2009

Joining Data Sources on Forms

Source: http://msdn.microsoft.com/en-us/library/aa608858.aspx

Joining Data Sources to Function as a Single Data Source:
Set the LinkType property on the secondary data source to InnerJoin, OuterJoin, ExistJoin, or NotExistJoin.

Joining Data Sources that have a Parent/Child Relationship:
Set the LinkType property on the child data source to Active, Passive, or Delayed.

LinkTypes:
  1. Passive
    Linked child data sources are not updated automatically.
    Updates of the child data source must be programmed on the active method of the master data source.

  2. Delayed
    A pause is inserted before linked child data sources are updated.
    This enables faster navigation in the parent data source because the records from child data sources are not updated immediately. For example, the user could be scrolling past several orders without immediately seeing each order lines.

  3. Active
    The child data source is updated immediately when a new record in the parent data source is selected.
    Continuous updates consume lots of resources.

  4. InnerJoin
    Selects records from the main table that have matching records in the joined table and vice versa.
    There is one record for each match.
    Records without related records in the other data source are eliminated from the result.

  5. OuterJoin
    Selects records from the main table whether they have matching records in the joined table.

  6. ExistJoin
    Selects a record from the main table for each matching record in the joined table.
    The differences between InnerJoin and ExistJoin are as follows:
    - When the join type is ExistJoin, the search ends after the first match has been found.
    - When the join type is InnerJoin, all matching records are searched for.

  7. NotExistJoin
    Select records from the main table that do not have a match in the joined table.

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