Default clause

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If the Default clause is present, the Data provider group will go to the Output only if the preceding Group (with the same name) is not present. 


<Default>::= [Default]


If you have a Taxes table:

Taxes ( TaxInitialDate*, TaxFinalDate*, TaxVAT, TaxIncome )

A Data Provider that returns the current tax values can be as follows:

   Where TaxInitialDate >= today()
   Where TaxFinalDate <= today() 
   VAT = TaxVAT 
   Income = TaxIncome 
CurrentTaxes [Default] 
   VAT = 0.7 
   Income = 0.3 

Here, the last Group will return the default values if there aren't any taxes in the period.

Note that the Default clause is equivalent to a When none in a For Each.

The default clause applies to all groups at the same level (brothers). The Default group is executed if none of the previous condition was satisfied.

Look at this in more detail with a sample. 

        Element where &a>3 { A=1 }
        Element where &a=5 { A=2 }
        Element [Default] where &a=2 { A=3 }
        Element [Default] { A=4 }

...and its behavior in runtime with some cases:

If &a=5 return two items (A=1 and A=2)

If &a=6 return one item (A=1)

If &a=2 return one item (A=3)

If &a=1 return one item (A=4)

Another sample, suppose you want to return a collection with the name of the products belonging to some Category or if not exist any product in the given category you want to return a text indicating ‘No products in the given category’.

You can write the following Data Provider:

      Where ProductCategoryId = &CategoryId
      ProductsInCategoryItem [Default]
            ProductName = 'No product in the given category'

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