Fields and Field Types

Fields and Field Types in ServiceNow

Why Fields and Field Types Are Important

Fields are the fundamental building blocks of data storage in ServiceNow. Every piece of information captured in the platform—from incident descriptions to user names—is stored in fields. Understanding field types is essential for database administrators and developers because selecting the appropriate field type ensures data integrity, proper validation, and optimal performance. For the CSA exam, this topic is crucial as it forms the foundation of data management in ServiceNow.

What Are Fields and Field Types?

A field is a column in a ServiceNow table that stores a specific type of data. Each field has a defined field type that determines what kind of data it can hold and how that data is displayed, validated, and stored.

Common Field Types in ServiceNow:

• String: Stores text data up to a specified maximum length (default 40 characters, max 4000)
• Integer: Stores whole numbers
• True/False: Boolean field storing yes/no or true/false values
• Reference: Creates a relationship to another table, storing the sys_id of the referenced record
• Date: Stores date values
• Date/Time: Stores both date and time values
• Choice: Provides a dropdown list of predefined options
• Journal: Stores timestamped entries that cannot be edited (like work notes and additional comments)
• Journal Input: Input field for adding new journal entries
• HTML: Stores formatted HTML content
• URL: Stores web addresses
• Currency: Stores monetary values
• Decimal: Stores numbers with decimal places
• Email: Stores email addresses with validation
• Phone Number: Stores telephone numbers
• Glide List: Stores multiple reference values from a single table

How Fields Work in ServiceNow

Fields are configured through the Dictionary (sys_dictionary table). When you create or modify a field, you define:

• Column name: The internal name used in scripts and queries
• Column label: The display name users see on forms
• Type: The field type determining data storage
• Max length: Maximum characters allowed (for string fields)
• Reference: Target table (for reference fields)
• Default value: Pre-populated value for new records
• Mandatory: Whether the field requires a value
• Read only: Whether users can modify the field

Creating Fields:
Navigate to the table using System Definition > Tables, select the table, and add fields in the Columns related list. Alternatively, use the form designer or personalize the form layout.

Reference Fields Deep Dive:
Reference fields are particularly important. They store only the sys_id of the referenced record, but can display any field from that record using dot-walking. For example, caller_id.email accesses the email of the user referenced in the caller_id field.

Exam Tips: Answering Questions on Fields and Field Types

• Remember that Journal fields are append-only—entries cannot be edited or deleted, making them ideal for audit trails

• Know the difference between String and Choice fields—String allows free-form text while Choice restricts input to predefined options

• Understand Reference field behavior—they store sys_id values, not the actual display value

• Glide List vs Reference—Glide List stores multiple references to the same table, while a standard Reference field stores only one

• Max length defaults—String fields default to 40 characters; know this for questions about data truncation

• Dictionary overrides—allow field attributes to be changed on extended tables; understand when to use table-level overrides versus dictionary entries

• When questions mention audit requirements or tracking changes over time, think Journal fields

• Questions about relationships between tables point to Reference fields

• For questions about data validation, consider how field types enforce data quality (Email validates format, Integer rejects text)

• Remember that changing a field type on an existing field can result in data loss—this is a common exam topic