Overriding Inherited Columns

Guide for using OverrideColumn to modify properties of columns inherited from a parent table. When you extend a table using extends, you inherit all columns from the parent. Use OverrideColumn to change how these inherited fields behave on the child table without modifying the parent table's definition.

When to Use

Use OverrideColumn for static/unconditional inherited field behavior:

• Making an inherited field mandatory on a child table while leaving it optional on the parent (unconditional — applies to ALL records)
• Changing the read-only behavior of an inherited field (e.g., making state always read-only in a specific child table)
• Setting static default values for inherited fields
• Filtering reference fields with static encoded queries (e.g., "active=true^roles=itil")
• Overriding calculation scripts for inherited calculated fields
• Changing dependent field settings on inherited fields
• Controlling whether an inherited field is displayed in the UI
• Modifying field attributes (edge encryption, sort behavior, display options)

Use Business Rules/UI Policies/Data Policies instead for conditional/dynamic behavior:

• Conditional enforcement: "mandatory if severity is Critical", "read-only if state is Closed"
• Dynamic filtering: "filter references based on current user's department" (use javascript: in referenceQualifier)
• Complex validation logic beyond mandatory/read-only
• Field value manipulation or calculations based on other fields

Do NOT use OverrideColumn when:

• Creating a new column (use the appropriate column type like StringColumn, ReferenceColumn, etc.)
• Adding fields to a table you don't extend (use regular column definitions or see the table-augments-guide topic)
• Modifying a field on the parent table itself (edit the parent table's definition directly)
• The field doesn't exist in any parent table (validate field existence first — see Field Validation section)

Instructions

1. Use OverrideColumn inside the table's schema: Dictionary overrides are defined directly in the Table object's schema property, using the inherited field name as the key. This requires the table to have extends set.
2. baseTable is optional: Omit baseTable when the field belongs to the table referenced in extends. Specify it explicitly when the field is defined further up the inheritance chain (e.g., task rather than incident).
3. Override selectively: Only set the properties you need to change. Unset properties inherit from the base table.
4. Table must extend a base table: OverrideColumn only works in tables that have extends. For non-extended tables, modify the field definition directly.
5. Import OverrideColumn: Import it from @servicenow/sdk/core alongside Table.

Key Concepts

OverrideColumn creates a sys_dictionary_override record in ServiceNow. This record modifies how an inherited column behaves on a child table without changing the parent table's column definition. The parent table and other child tables are unaffected.

Table inheritance requirements:

• The baseTable must be a parent table in the inheritance hierarchy
• The schema key (e.g., priority) must be a field defined in the base table
• The Table must have extends pointing to a table that is extensible

Available Override Properties

Property	Applies To	Description
mandatory	All fields	Make the field required or optional
default	All fields	Change the default value (use default, not defaultValue)
display	One field per table (display value)	Set this inherited field as the table's display value (primary identifier). Controls which column serves as the record's primary identifier, not UI visibility.
readOnlyOption	All fields	Control read-only access (see options below)
attributes	All fields	Change field attributes as a key-value object (e.g., { edge_encryption_enabled: true })
referenceQualifier	Reference fields	Filter reference field options using encoded queries or dynamic JavaScript qualifiers
dependent	Choice fields	Set dependent field for cascading selects
calculation	Calculated fields	Change the calculation script for calculated fields

Read-only options

The readOnlyOption property accepts the following values:

Use Case	Option	Behavior
Backwards compatibility (default)	'instance_configured'	System property controls behavior
UI read-only, allow all programmatic updates	'display_read_only'	Modified by Client scripts or server-side operations
UI read-only, only client scripts can update	'client_script_modifiable'	Client scripts allowed, server-side APIs blocked
Completely locked, no updates allowed	'strict_read_only'	All modifications prevented

Reference qualifier examples

When using referenceQualifier, you can:

• Use simple encoded queries: "active=true^roles=itil"
• Use dynamic qualifiers with javascript: prefix when filtering depends on:
  • Current record values: "javascript:'active=true^location=' + current.getValue('location')"
  • User context: "javascript:'active=true^department=' + gs.getUser().getDepartmentID()"
  • Complex business logic that cannot be expressed as a static query

🔍 Attribute Selection Guide

When using the attributes property in OverrideColumn, common available attributes can be found in the tables below organized by field type. Match attribute names exactly (case-sensitive) and use the correct value types.

Reference field attributes

Attribute	Value	Description
ref_ac_columns	semicolon-separated field names	Additional columns shown in the autocomplete dropdown (e.g., "name;email"). Requires ref_auto_completer: "AJAXTableCompleter".
ref_ac_columns_search	true/false	Enables autocomplete to search across all ref_ac_columns, not just the display value column.
ref_ac_display_value	true/false	Hides the display value column in autocomplete, showing only ref_ac_columns matches. Requires AJAXTableCompleter.
ref_ac_order_by	field name	Column used to sort the autocomplete list.
ref_auto_completer	JS class name	Custom autocomplete class. Options: AJAXReferenceCompleter (list, display value only), AJAXTableCompleter (table with extra columns), AJAXReferenceChoice (list, max 25 results).
ref_contributions	semicolon-separated UI macro names	Invokes the named UI macros when the reference field renders on a form.
ref_decoration_disabled	true/false	Disables the reference icon displayed next to a populated reference field.
ref_qual_elements	semicolon-separated field names	Fields sent back to the server to recalculate the reference qualifier dynamically.
ref_sequence	caret-separated field names (^)	Fields in the referenced table used to order the reference list (equivalent to ORDER BY).
tree_picker	true/false	Displays the reference field as a hierarchical tree (e.g., for location or category fields).
short_label	true/false	Shows the short label for a reference field (e.g., Email instead of Caller Email). Overrides the global glide.short.labels property.
long_label	true/false	Shows the long label for a reference field (e.g., Caller Email). Overrides the global glide.short.labels property.
slushbucket_ref_no_expand	true/false	Prevents users from expanding the reference in a form or list slush bucket.
allow_references	true/false	Displays a tree with reference fields so users can dot-walk when selecting a value.

List field attributes (glide_list)

Attribute	Value	Description
maintain_order	true/false	Shows up/down arrow buttons to reorder items in the list. Requires using the Add Multiple button.
no_multiple	true/false	Hides the select-multiple icons on a list field.
no_view	true/false	Hides the view-selected-item icon on a list field.
no_email	true/false	Removes the email box from a glide_list field referencing sys_user (e.g., Watch List).
start_locked	true/false	Sets the list field as locked by default. Set to false to unlock by default.
field_list_selector	true/false	Enables the user to select a field from the dependent table (or current table if no dependent is set).

String and text field attributes

Attribute	Value	Description
no_truncate	true/false	Shows the full text value in list views without truncation (default truncation is 40 characters).
html_sanitize	true/false	Enables or disables HTML sanitization on HTML/Translated HTML fields. Sanitization is on by default; set to false to disable.
strip_html_in_pdf	true/false	Strips HTML tags from the field value when exporting to PDF.
ro_collapsible	true/false	Adds an expand/collapse toggle icon next to a multiline field label.
allow_null	true/false	Allows the user to set the field value to None.
barcode	true/false	Enables a string field to use a mobile camera to scan and populate a barcode value.
knowledge_search	true/false	Shows a knowledge base search icon next to the field. Clicking it opens a knowledge search popup.
i18n_session_language_sortable	true/false	Enables sorting the column by the user's session language. When false, sorting follows the English alphabet.

Numeric and decimal field attributes

Attribute	Value	Description
scale	integer	Number of decimal places for a Decimal field. Default is 2. Requires maxLength to be increased accordingly (e.g., 4 decimal places needs maxLength > 15).
omit_sys_original	true/false	Skips retrieving the original value during calculations on price/currency fields, improving performance on high-volume tables.

General field attributes

Attribute	Value	Description
no_audit	true/false	Excludes this field from auditing even when the table is audited.
no_text_index	true/false	Prevents this field from being included in the table's text index.
isOrder	true/false	Sets this field as the default sort column in list views. Can be overridden by the ORDERBY URL parameter or user sort preferences.
user_preference	true/false	Uses the user's saved preferences for this field's default value instead of the system default.
ts_weight	integer	Controls the relative importance of text search matches in this field. Higher values rank this field's matches higher in search results.
ignore_filter_on_new	true/false	Prevents the field from auto-populating with values from a filtered list when creating a new record.
field_decorations	semicolon-separated UI macro names	Invokes the named UI macros when the field renders on a form. Similar to ref_contributions but for non-reference fields.
table	table name	For FieldListColumn — specifies which table's fields to populate the list from (e.g., "task").
vertical_layout	true/false	Displays radio button choices vertically instead of horizontally.
edge_encryption_enabled	true/false	Enables Edge Encryption for this field. Requires Edge Encryption to be configured on the instance.

⚠️ CRITICAL: Field validation and baseTable selection

You MUST validate that the field exists in the base table or any parent table before using OverrideColumn:

1. Start with the table specified in extends as the initial base table to check.
2. Query the instance for sys_dictionary filtered by name=<baseTable>^element=<element>
3. If the field doesn't exist in the current base table, check if that table extends another table by querying sys_db_object for name=<baseTable> and checking the super_class field.
4. If a parent table exists, recursively check for the field in the parent table by querying sys_dictionary filtered by name and element
5. Continue up the inheritance chain until the field is found or no more parent tables exist.
6. When the field is found, set baseTable in OverrideColumn to the table where the field was found (only if different from extends).
7. If the field is not found in any table in the inheritance chain, do NOT use OverrideColumn for that field. Instead, create a new field with the appropriate type in the table's schema.

Examples

Example 1: Making an Inherited Field Mandatory

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_custom_incident = Table({
  name: "x_myapp_custom_incident",
  extends: "incident",
  schema: {
    short_description: OverrideColumn({
      mandatory: true
    })
  }
});

Example 2: Changing Default Value

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_vip_task = Table({
  name: "x_myapp_vip_task",
  extends: "task",
  schema: {
    priority: OverrideColumn({
      default: "1"
    })
  }
});

Example 3: Overriding Reference Qualifier

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_special_incident = Table({
  name: "x_myapp_special_incident",
  extends: "incident",
  schema: {
    assignment_group: OverrideColumn({
      referenceQualifier: "roles=itil^active=true^type=support"
    })
  }
});

Example 3a: Advanced Reference Qualifier with Current Record Context

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_department_incident = Table({
  name: "x_myapp_department_incident",
  extends: "incident",
  schema: {
    assigned_to: OverrideColumn({
      baseTable: "task",
      referenceQualifier:
        "javascript:'active=true^department=' + current.getValue('u_department')"
    })
  }
});

Example 3b: Advanced Reference Qualifier with Dynamic Field Reference

import { Table, OverrideColumn } from "@servicenow/sdk/core";

// Note: location field is inherited from task table
export const x_myapp_location_incident = Table({
  name: "x_myapp_location_incident",
  extends: "incident",
  schema: {
    assigned_to: OverrideColumn({
      baseTable: "task",
      referenceQualifier:
        "javascript:'active=true^location=' + current.getValue('location')"
    }),
    assignment_group: OverrideColumn({
      referenceQualifier:
        "javascript:'active=true^u_location=' + current.getValue('location') + '^u_support_type=' + current.getValue('category')"
    })
  }
});

Example 4: Overriding Read-Only Option

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_approved_change = Table({
  name: "x_myapp_approved_change",
  extends: "change_request",
  schema: {
    state: OverrideColumn({
      readOnlyOption: "display_read_only" // appears read only, but can be modified by business rules and client script
    })
  }
});

Example 5: Changing Calculation

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_custom_user = Table({
  name: "x_myapp_custom_user",
  extends: "sys_user",
  schema: {
    name: OverrideColumn({
      calculation:
        "current.last_name + ', ' + current.first_name + ' (' + current.employee_number + ')'"
    })
  }
});

Example 6: Multiple Property Overrides

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_locked_task = Table({
  name: "x_myapp_locked_task",
  extends: "task",
  schema: {
    state: OverrideColumn({
      readOnlyOption: "strict_read_only", // strict read only, cannot be modified.
      mandatory: true,
      default: "1"
    })
  }
});

Example 7: Overriding Dependent Field

import { Table, OverrideColumn } from "@servicenow/sdk/core";

export const x_myapp_custom_incident = Table({
  name: "x_myapp_custom_incident",
  extends: "incident",
  schema: {
    subcategory: OverrideColumn({
      dependent: "u_custom_category"
    })
  }
});

Example 8: Changing Field Attributes (field on direct extends table)

import { Table, OverrideColumn } from "@servicenow/sdk/core";

// caller_id is defined on incident — no baseTable needed.
export const x_myapp_secure_incident = Table({
  name: "x_myapp_secure_incident",
  extends: "incident",
  schema: {
    caller_id: OverrideColumn({
      referenceQualifier: "active=true^department=IT",
      attributes: { ref_auto_completer: "AJAXTableCompleter" }
    })
  }
});

Example 9: baseTable Different from extends

When a table extends an intermediate table (e.g., incident extends task), and the field is defined on the grandparent, baseTable must point to the table where the field is actually defined — not the direct parent in extends.

import { Table, OverrideColumn } from "@servicenow/sdk/core";

// x_myapp_secure_incident extends incident, but description is defined on task.
// baseTable must be "task", not "incident".
export const x_myapp_secure_incident = Table({
  name: "x_myapp_secure_incident",
  extends: "incident",
  schema: {
    description: OverrideColumn({
      baseTable: "task",
      attributes: { edge_encryption_enabled: true }
    })
  }
});

Example 10: Complete Override with baseTable

import { Table, OverrideColumn, StringColumn } from "@servicenow/sdk/core";

export const x_myapp_custom_task = Table({
  name: "x_myapp_custom_task",
  extends: "task",
  schema: {
    assigned_to: OverrideColumn({
      baseTable: "task",
      mandatory: true,
      default: "javascript:gs.getUserID()",
      referenceQualifier: "active=true",
      attributes: { ref_auto_completer: "AJAXTableCompleter" }
    }),
    custom_field: StringColumn({ label: "Custom Field" })
  }
});

Avoidance

1. ⚠️ CRITICAL: Never create business rules, client scripts, or UI policies for static inherited field behavior that OverrideColumn supports — always prefer declarative overrides (mandatory, default, readOnlyOption, referenceQualifier, attributes) over imperative workarounds for unconditional requirements
2. Never use OverrideColumn for new columns — use the appropriate column type (StringColumn, ReferenceColumn, etc.) instead
3. Never omit baseTable on multi-level inheritance — when extending a table that itself extends another table, always specify which table defines the column
4. Never override a column that doesn't exist on the parent — the field must be validated to exist in the base table or any ancestor table before using OverrideColumn
5. Never use OverrideColumn without extends — if the table doesn't extend another table, there are no inherited columns to override
6. Never use attributes that don't exist in sys_schema_attribute table — the attribute must be defined in ServiceNow's attribute catalog

Related Topics

• overridecolumn-api — OverrideColumn API reference and property details
• table-guide — Creating and extending tables
• table-api — Full Table API reference
• referencecolumn-api — Creating new reference columns
• data-policy-guide — Conditional mandatory/read-only enforcement
• ui-policy-guide — Client-side field behavior