Reference Fields in ServiceNow are a fundamental concept that every Certified System Administrator must understand thoroughly. A Reference Field is a special field type that creates a relationship between two tables by storing a reference to a record in another table. Instead of storing actual data…Reference Fields in ServiceNow are a fundamental concept that every Certified System Administrator must understand thoroughly. A Reference Field is a special field type that creates a relationship between two tables by storing a reference to a record in another table. Instead of storing actual data values, Reference Fields store the sys_id (unique identifier) of a record from the referenced table.
When you create a Reference Field, you establish a many-to-one relationship between tables. For example, the Incident table has a Reference Field called 'Assigned to' that points to the User (sys_user) table. This allows each incident to be linked to a specific user record.
Key characteristics of Reference Fields include:
1. **Display Value vs. Actual Value**: The field displays a human-readable value (like a user's name) but stores the sys_id behind the scenes. This separation ensures data integrity even if the display value changes.
2. **Dot-Walking**: Reference Fields enable dot-walking, a powerful feature allowing you to access fields from the referenced table. For instance, incident.assigned_to.email retrieves the email address from the linked user record.
3. **Reference Qualifiers**: Administrators can restrict which records appear in the reference lookup using reference qualifiers, filtering options based on specific conditions.
4. **Auto-Complete**: Users benefit from auto-complete functionality when populating Reference Fields, making data entry efficient and accurate.
5. **Referential Integrity**: ServiceNow maintains relationships between records, though administrators must configure deletion rules to handle orphaned references appropriately.
From a database perspective, Reference Fields are stored as 32-character GUID strings (sys_id values). Understanding this storage mechanism is essential when writing queries, creating reports, or performing data migrations. Reference Fields form the backbone of ServiceNow's relational data model, enabling complex workflows, reporting relationships, and seamless navigation between related records throughout the platform.
Reference Fields in ServiceNow - Complete CSA Exam Guide
What are Reference Fields?
Reference fields are a special field type in ServiceNow that create relationships between tables by storing a reference to a record in another table. Instead of storing actual data, a reference field stores the sys_id (unique 32-character identifier) of a record from the referenced table.
Why Reference Fields are Important
Reference fields are fundamental to ServiceNow's relational database structure. They:
• Enable data normalization by eliminating redundant data storage • Create relationships between different tables (like linking incidents to users) • Allow efficient data retrieval across related records • Support dot-walking to access fields from referenced records • Maintain data integrity through consistent relationships
How Reference Fields Work
When you create a reference field, you must specify which table it references. For example, the Caller field on the Incident table references the User (sys_user) table.
Key Technical Details:
• Stored Value: The sys_id of the referenced record is stored in the database • Display Value: Users see a human-readable value (usually the display value of the referenced record) • Reference Qualifier: Filters which records can be selected in the reference field • Reference Icon: The small 'i' icon next to reference fields allows users to preview referenced record details
Dot-Walking with Reference Fields
One of the most powerful features is dot-walking, which allows you to access fields from referenced tables. For example:
• caller_id.email - accesses the email of the caller on an incident • caller_id.department.name - accesses the department name of the caller
Reference qualifiers limit which records appear in the reference field lookup. Types include:
• Simple: active=true • Dynamic: Uses JavaScript to build the query • Advanced: Uses script includes for complex filtering
Exam Tips: Answering Questions on Reference Fields
1. Remember the sys_id: Reference fields always store the sys_id, not the display value. This is a frequently tested concept.
2. Understand dot-walking syntax: Know that you use periods to navigate through reference fields to access related data.
3. Display vs. Value: When questions ask what is stored versus what is displayed, remember: sys_id is stored, display value is shown to users.
4. Reference qualifiers: Understand that these filter available choices in reference field lookups.
5. Look for keywords: Questions mentioning 'relationship between tables,' 'linked records,' or 'accessing data from another table' often relate to reference fields.
6. Performance considerations: Reference fields with dot-walking in list views can impact performance - this may appear in scenario-based questions.
7. Field type recognition: On the exam, if you see a field that allows selecting a record from another table, identify it as a reference field.
8. Common trap: Do not confuse reference fields with glide lists (which store multiple references) or document ID fields.
Practice Scenario
If asked: 'What value is stored when a user selects a caller on an incident record?'
The correct answer involves the sys_id of the selected user record being stored in the caller_id field, while the user's name is displayed to provide a user-friendly interface.