Understanding Relationship Fields and Polymorphic Fields

Some fields are relationship fields, which means they can be used to get information about a related object. And some of those relationship fields are polymorphic fields. A polymorphic field is one where the related object might be one of several different types of objects. For example, the Who relationship field of a Task can be a Contact or a Lead.

Example of a Relationship Field

1SELECT Id, Owner.Name FROM Account

Example of a Polymorphic Field

This means it is a polymorphic field. Owner could be a Calendar, or a User. For example, you can use the following SOQL query:

1SELECT Id, Owner.Name FROM Event WHERE Owner.Type = 'User'

Using Polymorphic Fields

Common Polymorphic Fields

Common polymorphic fields include:

• Owner: This field represents the parent of the record. For example:
  1SELECT Id, Owner.Name
  2FROM Task
  3WHERE Owner.FirstName like 'B%'

  This example query works for Task records whose owners are either Calendars or Users.

• Who: This field represents the person associated with the record. For example:
  1SELECT Id, Who.FirstName, Who.LastName
  2FROM Task
  3WHERE Owner.FirstName LIKE 'B%'

  This example query works for Task records whose owners can be either Calendars or Users, and whose Who field can be either Contacts or Leads.

  If you'd like to know the type of object returned in a query, use Who.Type. For example:

  1SELECT Id, Who.Id, Who.Type
  2FROM Task

  Using this example, you can query all the Tasks associated with Contacts:

  1SELECT Id, Who.Id, Who.Type
  2FROM Task
  3WHERE Who.Type='Contact'

• What: This field represents nonhuman objects that are associated with the record. For example:
  1SELECT Id, What.Name
  2FROM Event

  This example query works for Events where What can be an Account or a Solution, or any of another number of object types.

Using the Type Qualifier

1SELECT Id
2FROM Event
3WHERE What.Type IN ('Account', 'Opportunity')

Using TYPEOF

SOQL supports polymorphic relationships using the TYPEOF expression in a SELECT statement. TYPEOF is available in API version 46.0 and later. (It is also available in API version 26.0 and later as part of a Developer Preview.)

1SELECT 
2  TYPEOF What
3    WHEN Account THEN Phone, NumberOfEmployees
4    WHEN Opportunity THEN Amount, CloseDate
5    ELSE Name, Email
6  END
7FROM Event

Note the following considerations for TYPEOF.

• TYPEOF can’t be used with a relationship field whose namePointing attribute is false.
• TYPEOF can’t be used with a relationship field whose relationshipName attribute is false.
• TYPEOF is only allowed in the SELECT clause of a query. You can filter on the object type of a polymorphic relationship using the Type qualifier in a WHERE clause. For details, see Filter on Polymorphic Relationship Fields.
• TYPEOF isn’t allowed in queries that don’t return objects, such as COUNT() .
• TYPEOF can’t be used in SOQL queries that are the basis of Streaming API PushTopics.
• TYPEOF can’t be used in SOQL used in Bulk API.
• TYPEOF expressions can’t be nested. For example, you can’t use TYPEOF inside the WHEN clause of another TYPEOF expression.
• TYPEOF isn’t allowed in the SELECT clause of a semi-join query. You can use TYPEOF in the SELECT clause of an outer query that contains semi-join queries. The following example is not valid because TYPEOF is used in the semi-join query:
  1SELECT Name FROM Account
  2WHERE CreatedById IN
  3    (
  4    SELECT 
  5        TYPEOF Owner
  6            WHEN User THEN Id
  7            WHEN Group THEN CreatedById
  8        END
  9    FROM CASE
  10    )

  The following example is valid because TYPEOF is only used in the outer SELECT clause:
  1SELECT 
  2    TYPEOF What
  3        WHEN Account THEN Phone
  4        ELSE Name
  5    END
  6FROM Event
  7WHERE CreatedById IN
  8    (
  9    SELECT CreatedById
  10    FROM Case
  11    )

• TYPEOF can’t be used in queries with functions in the SELECT clause. The following example is not valid because the TYPEOF includes the FORMAT function.
  1SELECT
  2 TYPEOF What
  3  WHEN Account THEN Id, FORMAT(LastModifiedDate) LastModifiedDate__f
  4  WHEN Opportunity THEN Id
  5 END
  6FROM Task

  Instead, run the same query without functions to retrieve a list of IDs.
  1SELECT
  2    TYPEOF What
  3        WHEN Account THEN Id, LastModifiedDate
  4        WHEN Opportunity THEN Id
  5    END
  6FROM Task

  Then, run a second query with functions on the resulting ID list.
  1SELECT 
  2    FORMAT(LastModifiedDate) LastModifiedDate__f 
  3FROM Account 
  4WHERE Id in RetrievedIdList

• TYPEOF can’t be used in queries with GROUP BY, GROUP BY ROLLUP, GROUP BY CUBE, and HAVING.

Combining TYPEOF and Type

1SELECT Id,
2  TYPEOF What
3    WHEN Account THEN Phone
4    WHEN Opportunity THEN Amount
5  END
6FROM Event
7WHERE What.Type IN ('Account', 'Opportunity')

Object Types in WSDLs

1private com.sforce.soap.enterprise.sobject.SObject Owner;