Schema Map & Table Relationships

ServiceNow’s Schema Maps make it easier to identify and find data structures. The topic focuses on the schema map, an ideal visualization tool for depicting the structural relationships between tables. It also highlights the mechanism of extended tables, which allow admins to build scalable data structures. 

Schema Map

The ServiceNow schema map is a visual tool that helps you understand how tables are connected. The inter-table relationships include many-to-many, extended, and referenced tables via reference fields. 

How to see schema map in ServiceNow:

1. Go to System Definition → Tables

2. Open the table you want to examine (e.g., incident)

3. Click Schema Map

It opens an interactive diagram showing the servicenow table schema map:

• Tables that extend the current table.
• Tables referenced by fields.
• Tables that reference the current one.

It is one of the best ways to understand how data flows between tables—especially when designing custom applications or debugging complex setups. 

Exporting Table Schema

In the ServiceNow export table schema, you can get documentation, review, or planning features. You can also use built-in platform features:

• Use the Dictionary to export a table’s field structure.
• Export table lists as Excel or XML for review.
• Use scripts to export schema data programmatically (for advanced cases).

While there’s no “one-click schema exporter,” combining dictionary and list views allows you to share table structures with teams or clients efficiently.

ServiceNow CMDB Schema Map 

The CMDB schema map is a series of connected tables that admins control to track Configuration items. This service now schema map displays the database links and suggested relationships, for example, runs on, depends on, and is connected to. 

The CMDB schema map lets admins see if the database server goes down and how the web app and user portal are affected. 

Extended Table and Referenced Tables

Extended Table

Table extension allows you to reuse existing fields, logic, and behaviour from a parent table. It is like a parent-child relationship where the child inherits everything from the parent. sys_class_name system field tells the database which table classification the record belongs to.

How to extend a table in servicenow:

1. While creating the table, fill the Extends Table field
2. Select a parent table (like task or sys_user)
3. Submit the form

Table extension in ServiceNow is a core part of the platform architecture. If any changes are made to the parent (task), they will affect and appear on the child (incident, problem, or change).

Referenced Tables in ServiceNow 

ServiceNow has referenced tables, where Table A stores the sys_id of a record in Table B. Unlike extended tables, referenced tables do not inherit fields; these are like pointer tables that refer incidents to users. 

For example, think of it like a hotel key card: a ServiceNow incident, and you are the user. It refers to your room, but it’s not the room itself. 

• Incident “Assignment Group” references sys_user_group.

What’s Next? 

In the next topic, we will be focusing on the data dictionary and how choice lists work in ServiceNow.

Next Topic