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Saravanan View Drop Down
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Joined: 08-Dec-2007
Location: India
Posts: 12 		Post Options Post Options   Quote Saravanan Quote  Post ReplyReply Direct Link To This Post Topic: EntityRelations
    Posted: 14-Dec-2007 at 4:29am
Hello sir,
How to multiple table join and table columns is manually added in gridview.column added for manually.
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davidklitzke View Drop Down
IdeaBlade
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Joined: 14-Jun-2007
Posts: 715 		Post Options Post Options   Quote davidklitzke Quote  Post ReplyReply Direct Link To This Post Posted: 14-Dec-2007 at 10:56am
If you are looking for an example of a table join in DevForce, we don't do them because they are not necessary.  Here is a paragraph from the ConCepts Manual.
Why we don’t need JOINs

OQL uses subqueries instead of joins for filtering based on values in related data source objects. We would use a subquery relating Employee to Address in order to limit the employees to residents of California. Joins and subqueries are functionally equivalent and perform equally well in all industry-leading databases. They also translate more directly to capabilities of non-relational data sources.

We don’t want to use joins to merge fields from different tables. We don’t want the PersistenceManager to return an ad hoc mix of data from the Employee and Address tables[1].  When we need the employee’s home state we will use entity navigation[2] and write anEmployee.HomeAddress.State instead.

[1]     See the “Mapping to Multiple Tables” and “Gloom With a View” topics in the “Advanced Business Object Concepts” section.

[2]     The entity navigation discussion is coming up shortly.
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