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This function determines the intersection of two collections. It returns a collection containing the items that are present in both specified collections.

Syntax

Code Block
INTERSECTION ( collection1 , collection2 )
  • collection1, collection2 - Collections to be intersected. These collections must be of the same base type.

Return type

  • collection

Examples

Suppose the following model. Entity Teacher has a multivalued relation with entity Child via the relation Teacher.teaches_Children.

 

Teacher instanceChild instanceChild.nameChild.hobbies
Teacher_1Child_1“Kim”“Reading”, “Dancing”
Teacher_1Child_2“Rick”“Tennis”, “Dancing”
Teacher_1Child_3“Bob”“Painting”, “Basketball”, “Reading”
Teacher_2Child_1“Kim”“Reading”, “Dancing”
Teacher_2Child_3“Bob”“Painting”, “Basketball”, “Reading”
Teacher_2Child_4“Mary”“Football”

 

  • INTERSECTION ( Teacher[Teacher_1].teaches_Children , Teacher[Teacher_2].teaches_Children ) results in a collection of child Child instances Child_1 and Child_3
  • INTERSECTION ( Teacher[Teacher_1].teaches_Children.name , Teacher[Teacher_2].teaches_Children.name ) results in a  = “Kim”, “Bob”
  • INTERSECTION ( Child[Child_1].hobbies , Child[Child_3].hobbies ) results in = “Reading”
  • INTERSECTION ( Child[Child_2].hobbies , Child[Child_3].hobbies ) results in an empty list

Collections vs. lists

UNIQUE, SUBSET, UNION and INTERSECTION return a collection of data, i.e. double entries are removed. However, COLLECT statements, + and - return a list of data. You have to be aware of this when using the SIZE or UNPACK function.

Example

Statuses = ["a","b","c","d","a","b","c","d"].

Result

The expression "SIZE ( COLLECT Status FROM {Statuses} )" will result in 8. Note that duplicates are not removed.

The expression "SIZE ( UNIQUE ( COLLECT Status FROM {Statuses} ) )" will result in 4, as the unique filters the duplicates.

UI Text Box
typewarning

When the expression is completely evaluated, all duplicates are filtered as well. Using COLLECT Status FROM {Statuses} as a default expression on an attribute, will result in 4 elements.