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Learn more about the functions ISNULLfunctions ISNULL, ISUNKNOWN, IFUNKOWNIFUNKNOWN, IS A, TYPE OF, ISACTIVE, GUID. toc
Overview
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| Function | Description |
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| Checks whether a value is unknown |
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Syntax
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ISNULL ( expression ) |
- expression - Expression that is checked.
Return type
- boolean - TRUE of the attribute is unknown, FALSE otherwise
Examples
Suppose the following data model.
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ISUNKNOWN | Replaces |
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ISUNKNOWN
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| a value if that value is unknown. |
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Syntax
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ISUNKNOWN ( expression , value ) |
- expression- Expression of which the value has to be returned if that value is known.
- value - Value to return if the expression value is unknown.
Return type
- any type, equals the expression type
Examples
Suppose the following data model.
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IFUNKNOWN | Alternative notation of the ISUNKNOWN |
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Both parameters of the
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IFUNKNOWN
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| function, which increases readability especially for long expressions |
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The IFUNKNOWN function takes precendence over any other binary operator (except for the "NOT" operator).
For example, this means that the expression A.B AND C.D IFUNKNOWN FALSE will be interpreted as A.B AND (C.D IFUNKNOWN FALSE). You can use parentheses to influence this behavior, e.g. by writing (A.B AND C.D) IFUNKNOWN FALSE.
For the "NOT" operator the following expression "X AND NOT B IFUNKNOWN FALSE", can also be read as "X AND ((NOT B) IFUNKNOWN FALSE)"
Syntax
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expression IFUNKNOWN value |
expression- Expression of which the value has to be returned if that value is known.
value - Value to return if the expression value is unknown.
Return type
any type, equals the expression type
Examples
Suppose the following data model.
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Both parameters of the IFUNKNOWN function must be of the same datatype. If they differ in datatype, you get this validation error in studio:
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| Checks the entity type of an |
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Syntax
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instance IS A entity_name |
| instance |
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entity_name - Name of the entity as string.
Return type
- boolean
Examples
Suppose a domain model in which there is a singleton entity Residence that has a multivalued relation hasRooms with Room. Room is the base entity for singleton Kitchen and not singletons Bedroom and Bathroom.
If you want to determine the number of bedrooms is the residence:
COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bedroom” ) )
If you want to determine the number of bathrooms is the residence:
COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bathroom” ) )
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TYPE OF
Use this function to determine the type of an instance. The function returns the name of the entity.
Syntax
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TYPE OF base_entity |
- base_entity - Name of the instance's base entity.
Return type
- string
Examples
Suppose a domain model in which there is a singleton entity Residence that has a multivalued relation hasRooms with Room. Room is the base entity for singleton Kitchen and not singletons Bedroom and Bathroom.
- for the
Kitcheninstance the expression( TYPE OF Room ) = “Kitchen” - for the
Bedroominstances the expression( TYPE OF Room ) = “Bedroom”
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ISACTIVE
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| if an instance of a specific entity type is currently |
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ISACTIVE instances [WHERE condition] |
- instances - instances to search
- condition - optional condition to limit the collection of instances to check
Return type
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Singletons are always active, so |
Examples
Suppose the following data model.
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GUID
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GUID | Generates a globally unique identifier which can later be used to uniquely mark and recognize a desired element. |
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Functions
Include Page Miscellaneous function ISNULL Miscellaneous function ISNULL
Include Page Miscellaneous function ISUNKNOWN Miscellaneous function ISUNKNOWN
Include Page Miscellaneous function IFUNKNOWN Miscellaneous function IFUNKNOWN
Include Page Miscellaneous function IS A Miscellaneous function IS A
Include Page Miscellaneous function TYPE OF Miscellaneous function TYPE OF
Include Page Miscellaneous function ISACTIVE Miscellaneous function ISACTIVE
Include Page Miscellaneous function GUID Miscellaneous function GUID
The GUIDs are represented as 32 hexadecimal digits, displayed in five groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters.
Syntax
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GUID() |
Return type
String - the generated GUID
Examples
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Overview
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