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Enforce Join

I want to know the difference between the different types of enforce join:

-Not enforced
-Enforced From
-Enforced To
-Enforced Both

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MKItani
Asked:
MKItani
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6 Solutions
 
Raja Jegan RSQL Server DBA & ArchitectCommented:
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MKItaniAuthor Commented:
i read these article before but it is not clear at all,
So please any body can send me a real example or an explanation more effective.
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GhunaimaCommented:
For details & Example of Types of Joins in SQL server Go to
http://www.mssqltips.com/tip.asp?tip=1667
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KrtyknmCommented:
Enforcing joins are used in SQL server to optimize the query, below link will help you to identify
http://msdn.microsoft.com/en-us/library/ms173815.aspx
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Raja Jegan RSQL Server DBA & ArchitectCommented:
>> i have choiced the false category.

Instead of deleting this question, you can request Moderators to add this question into Crystal Reports zone.
Now that I have objected, Moderators can add this question to appropriate zones.
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MKItaniAuthor Commented:
Please remove this question form ms SQL SERVER CATEGORY to Crystal report category
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mlmccCommented:
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mlmccCommented:
A real example

Consider an Order system

Order Table
OrderId                CustomerId                   OrderDate                  ShipDate
   1                            1                               1 May 2011               4May 2011
   2                            3                               3 May 2011               6 May 2011
   3                            4                               8 May 2011
   4                            5                               11 May 2011

Order Detail Table
OrderDetailId      fkOrderId        ProductId     Quantity        
     1                           1                   P1                2
      2                           1                  P2                 1
     3                            2                  P1                 10
     4                            2                  P4                 1
      5                           3                  P2                 1
     6                            5                  P5                 2

Customer Table
CustomerId   Name            Address            City      
     1                J Smith          11 Some St      SunCity
     2                B Jones         12 Another Ave   NewCity
     3                K Doe             15  A St             SomeCity
     5                J Doe              20 A St              Some City

  Select Order.* FROM Order INNER JOIN OrderDetail ON Order.OrderId = OrderDetail.fkOrderId

Not Enforced - 4 records are returned   - No fields from Order Detail selected so it is ignored.  Same as
Select Order.* FROM Order

Enforced       - 3 records are returned   OrderIds 1,2,3  OrderId 4 is not returned because there is no matching record in the detail table.

Enforced From - 4 records returned.  Ignored since no fields from OrderDetail selected

Enforced To - 3 records returned same as Enforced

Another example
Select OrderDetail.* FROM Order INNER JOIN OrderDetail ON Order.OrderId = OrderDetail.fkOrderId

Not Enforced - 6 records returned.  Same as Select OrderDetail.* FROM OrderDetail

Enforced   - 5 records returned.   OrderDetail 1 - 5  All have match in Order table

Enforced From - Same as Enforced

Enforced To - Same as not enforced

mlmcc


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