Tables and classes

A table can "extend" another table. A table that extends another table is called a child class, and the table it extends is the parent class.

Some tables are both a parent and child class because they extend and are extensions of other tables. A parent class that is not an extension of another table is called a base class.

The dictionary entry for a child class only contains the fields unique to the child class. The fields inherited from the parent class belong to the dictionary entry for the parent class. This means that a child class record has values in both the child class and all of its parent classes. The full child class record is actually a collection of values from multiple tables that all share the same sys_id value. The system tracks record changes by the sys_id value and applies any change to all classes that have a record with the matching sys_id value. For example, if you delete an incident record, the system also deletes the corresponding record in the task table.

The following video provides an introduction to tables in ServiceNow.

To see the relationships between classes, use the schema map.

The following is a table of tables in the platform that extend other tables:
Note: If a table is not included here, it does not extend another table.
Table 1. Tables that are extensions of other tables
Table Name Label Extension of Label
ast_lease Lease ast_contract Contract
ast_license_adobe Adobe Software License ast_license_base Base License Table
ast_license_generic Generic Software License ast_license_base Base License Table
ast_license_msft Microsoft Software License ast_license_base Base License Table
ast_license_symantec Symantec Software License ast_license_base Base License Table
ast_service Service Contract ast_contract Contract
ast_warranty Warranty ast_contract Contract
bsm_action BSM Map Actions diagrammer_action Diagrammer Actions
catalog_script_client Catalog Client Scripts sys_script_client Client Script
catalog_ui_policy Catalog UI Policy sys_ui_policy UI Policy
catalog_ui_policy_action Catalog UI Policy Action sys_ui_policy_action UI Policy Action
change_phase Change Phase task Task
change_request Change Request task Task
change_request_imac IMAC change_request Change Request
change_task Change Task task Task
cmdb_ci_acc Accessory cmdb_ci Configuration Item
cmdb_ci_aix_server AIX Server cmdb_ci_unix_server Unix Server
cmdb_ci_apache_web_server Apache Web Server cmdb_ci_web_server Web Server
cmdb_ci_appl Application cmdb_ci Configuration Item
cmdb_ci_application_software Application Software cmdb_ci_spkg Software
cmdb_ci_app_server Application Server cmdb_ci_appl Application
cmdb_ci_app_server_domino Domino cmdb_ci_app_server Application Server
cmdb_ci_app_server_java Java Server cmdb_ci_app_server Application Server
cmdb_ci_app_server_jboss Jboss cmdb_ci_app_server Application
cmdb_ci_app_server_tomcat Tomcat cmdb_ci_app_server Application Server
cmdb_ci_app_server_weblogic BEA Weblogic cmdb_ci_app_server Application Server
cmdb_ci_app_server_websphere IBM Websphere cmdb_ci_app_server Application Server
cmdb_ci_business_process Business Process cmdb_ci Configuration Item
cmdb_ci_circuit Circuit cmdb_ci Configuration Item
cmdb_ci_cluster Cluster cmdb_ci Configuration Item
cmdb_ci_cluster_node Cluster Node cmdb_ci Configuration Item
cmdb_ci_cluster_resource Cluster Resource cmdb_ci Configuration Item
cmdb_ci_cluster_vip Cluster Virtual IP cmdb_ci Configuration Item
cmdb_ci_comm Communication Device cmdb_ci Configuration Item
cmdb_ci_computer Computer cmdb_ci Configuration Item
cmdb_ci_computer_room Computer Room cmdb_ci Configuration Item
cmdb_ci_crac Computer Room AC cmdb_ci Configuration Item
cmdb_ci_database Database cmdb_ci Configuration Item
cmdb_ci_datacenter Data Center cmdb_ci Configuration Item
cmdb_ci_db_catalog Database Catalog cmdb_ci Configuration Item
cmdb_ci_db_db2_catalog DB2 Catalog cmdb_ci_db_catalog Database Catalog
cmdb_ci_db_db2_instance DB2 Instance cmdb_ci_db_instance Database Instance
cmdb_ci_db_instance Database Instance cmdb_ci_appl Application
cmdb_ci_db_mssql_catalog MSFT SQL Catalog cmdb_ci_db_catalog Database Catalog
cmdb_ci_db_mssql_instance MSFT SQL Instance cmdb_ci_db_instance Database Instance
cmdb_ci_db_mysql_catalog MySQL Catalog cmdb_ci_db_catalog Database Catalog
cmdb_ci_db_mysql_instance MySQL Instance cmdb_ci_db_instance Database Instance
cmdb_ci_db_ora_catalog Oracle Catalog cmdb_ci_db_catalog Database Catalog
cmdb_ci_db_ora_instance Oracle Instance cmdb_ci_db_instance Database Instance
cmdb_ci_db_syb_catalog Sybase Catalog cmdb_ci_db_catalog Database Catalog
cmdb_ci_db_syb_instance Sybase Instance cmdb_ci_db_instance Database Instance
cmdb_ci_desktop_software Desktop Software cmdb_ci_spkg Software
cmdb_ci_directory_server Directory Server cmdb_ci_infra_service Infrastructure Service
cmdb_ci_disk Disk cmdb_ci Configuration Item
cmdb_ci_email_server Email Server cmdb_ci_infra_service Infrastructure Service
cmdb_ci_esx_server ESXi Server cmdb_ci_server Server
cmdb_ci_file_system File System cmdb_ci Configuration Item
cmdb_ci_file_system_nfs NFS File System cmdb_ci_file_system File System
cmdb_ci_file_system_smb SMB File System cmdb_ci_file_system File System
cmdb_ci_ftp_server FTP Server cmdb_ci_infra_service Infrastructure Service
cmdb_ci_group Group cmdb_ci Configuration Item
cmdb_ci_hpux_server HPUX Server cmdb_ci_unix_server Unix Server
cmdb_ci_infra_service Infrastructure Service cmdb_ci_appl Application
cmdb_ci_infra_service_ldap LDAP Service cmdb_ci_infra_service Infrastructure Service
cmdb_ci_inf_software Infrastructure Software cmdb_ci_spkg Software
cmdb_ci_ip_device IP Device cmdb_ci Configuration Item
cmdb_ci_ip_network IP Network cmdb_ci Configuration Item
cmdb_ci_ip_phone IP Phone cmdb_ci Configuration Item
cmdb_ci_ip_router IP Router cmdb_ci_netgear Network Gear
cmdb_ci_ip_server IP Server cmdb_ci_infra_service Infrastructure Service
cmdb_ci_ip_service IP Service cmdb_ci Configuration Item
cmdb_ci_ip_switch IP Switch cmdb_ci_netgear Network Gear
cmdb_ci_iplanet_web_server iPlanet Web Server cmdb_ci_web_server Web Server
cmdb_ci_linux_server Linux Server cmdb_ci_server Server
cmdb_ci_mainframe IBM Mainframe cmdb_ci_server Server
cmdb_ci_mainframe_lpar IBM Mainframe LPAR cmdb_ci_server Server
cmdb_ci_microsoft_iis_web_server Microsoft IIS Web Server cmdb_ci_web_server Web Server
cmdb_ci_msd Storage Device cmdb_ci Configuration Item
cmdb_ci_netgear Network Gear cmdb_ci Configuration Item
cmdb_ci_netware_server Netware Server cmdb_ci_server Server
cmdb_ci_network_adapter Network Adapter cmdb_ci Configuration Item
cmdb_ci_net_traffic Network Traffic cmdb_ci Configuration Item
cmdb_ci_nginx_web_server NGINX Web Server cmdb_ci_web_server Web Server
cmdb_ci_osx_server OS/X Server cmdb_ci_server Server
cmdb_ci_patches Patch cmdb_ci Configuration Item
cmdb_ci_pdu PDU cmdb_ci Configuration Item
cmdb_ci_pdu_outlet Outlet cmdb_ci Configuration Item
cmdb_ci_peripheral Computer Peripheral cmdb_ci Configuration Item
cmdb_ci_printer Printer cmdb_ci Configuration Item
cmdb_ci_print_queue Print Queue cmdb_ci Configuration Item
cmdb_ci_rack Rack cmdb_ci Configuration Item
cmdb_ci_server Server cmdb_ci_computer Computer
cmdb_ci_service Business Service cmdb_ci Configuration Item
cmdb_ci_snc_component SNC Component cmdb_ci Configuration Item
cmdb_ci_solaris_server Solaris Server cmdb_ci_unix_server Unix Server
cmdb_ci_spkg Software cmdb_ci Configuration Item
cmdb_ci_tomcat_connector Tomcat Connector cmdb_ci Configuration Item
cmdb_ci_unix_daemon Unix Daemon cmdb_ci_ip_service IP Service
cmdb_ci_unix_server Unix Server cmdb_ci_server Server
cmdb_ci_ups UPS cmdb_ci Configuration Item
cmdb_ci_ups_alarm UPS Alarm cmdb_ci Configuration Item
cmdb_ci_ups_bypass UPS Bypass cmdb_ci Configuration Item
cmdb_ci_ups_input UPS Input cmdb_ci Configuration Item
cmdb_ci_ups_output UPS Output cmdb_ci Configuration Item
cmdb_ci_vm Virtual Machine cmdb_ci Configuration Item
cmdb_ci_vm_parallels Parallels cmdb_ci_vm Virtual Machine
cmdb_ci_vm_vmware VMware cmdb_ci_vm Virtual Machine
cmdb_ci_vm_zones Zones cmdb_ci_vm Virtual Machine
cmdb_ci_vpn Virtual Private Network cmdb_ci Configuration Item
cmdb_ci_websphere_cell Websphere Cell cmdb_ci Configuration Item
cmdb_ci_web_application Web Application cmdb_ci_appl Application
cmdb_ci_web_server Web Server cmdb_ci_infra_service Infrastructure Service
cmdb_ci_web_service Web Service cmdb_ci_appl Application
cmdb_ci_web_site Web Site cmdb_ci_appl Application
cmdb_ci_windows_service Windows Service cmdb_ci_ip_service IP Service
cmdb_ci_win_cluster Windows Cluster cmdb_ci_cluster Cluster
cmdb_ci_win_cluster_node Windows Cluster Node cmdb_ci_cluster_node Cluster Node
cmdb_ci_win_cluster_resource Windows Cluster Resource cmdb_ci_cluster_resource Cluster Resource
cmdb_ci_win_server Windows Server cmdb_ci_server Server
cmdb_ci_zone Zone cmdb_ci Configuration Item
cmdb_metric_cpu CI CPU Metrics cmdb_metric CI Metric
cmdb_metric_db_connections CI DB Connection Metric cmdb_metric CI Metric
cmdb_metric_errors Errors Logged cmdb_metric CI Metric
cmdb_metric_events_processed Events Processed cmdb_metric CI Metric
cmdb_metric_event_logs Events Logged cmdb_metric CI Metric
cmdb_metric_java CI Java Metric cmdb_metric CI Metric
cmdb_metric_linux_memory Linux Memory Metrics cmdb_metric CI Metric
cmdb_metric_load CI Load Metrics cmdb_metric CI Metric
cmdb_metric_logs CI Log Count cmdb_metric CI Metric
cmdb_metric_mysql_statements CI MySQL Metrics cmdb_metric CI Metric
cmdb_metric_oracle CI Oracle Metrics cmdb_metric CI Metric
cmdb_metric_partition Partition Read/Write Statistics cmdb_metric CI Metric
cmdb_metric_semaphores CI Semaphore Metrics cmdb_metric CI Metric
cmdb_metric_service_now CI Service-Now Metrics cmdb_metric CI Metric
cmdb_metric_sql SQL Response Metrics cmdb_metric CI Metric
cmdb_metric_transactions CI Transaction Metrics cmdb_metric CI Metric
discovery_probes_multi Multiprobe discovery_probes Probe
discovery_probes_snmp SNMP Probe discovery_probes Probe
discovery_probes_wmi WMI Probe discovery_probes Probe
ecc_agent_counter_metric ECC Agent Counter Metric ecc_agent_metric ECC Agent Metric
ecc_agent_memory_metric ECC Agent Memory Metric ecc_agent_metric ECC Agent Metric
ecc_agent_rgr_metric ECC Agent RGR Metric ecc_agent_metric ECC Agent Metric
ecc_agent_scalar_metric ECC Agent Scalar Metric ecc_agent_metric ECC Agent Metric
expert_panel_catalog_checkout Catalog Checkout Panel expert_panel Wizard Panel
expert_panel_catalog_order Catalog Order expert_panel Wizard Panel
expert_panel_knowledge KB Viewer expert_panel Wizard Panel
expert_panel_template Record Generator expert_panel Wizard Panel
expert_script_client Wizard Client Script sys_script_client Client Script
expert_variable Wizard Variable question Question
import_log Import Log syslog Log Entry
imp_computer Computer sys_import_set_row Import Set Row
imp_location Location sys_import_set_row Import Set Row
imp_notification Notification sys_import_set_row Import Set Row
imp_user User sys_import_set_row Import Set Row
incident Incident task Task
item_option_new Variable question Question
kb_submission KB Submission task Task
ola OLA sla SLA
plan_mysql Plan MySQL plan_execution Plan Execution
plan_oracle Plan Oracle plan_execution Plan Execution
problem Problem task Task
process_step_approval Approval Steps process_step Process Steps
release_phase Release Phase task Task
release_task Release Task task Task
scheduled_data_import Scheduled Data Import sysauto Scheduled Job
scheduled_import_set Scheduled Data Import scheduled_data_import Scheduled Data Import
sc_category_top_n Dynamic Category sc_category Category
sc_cat_item_content Content Item sc_cat_item Catalog Item
sc_cat_item_dt_approval Execution Plan Approval Task sc_cat_item_delivery_task Execution Plan Task
sc_cat_item_guide Order Guide sc_cat_item Catalog Item
sc_cat_item_producer Record Producer sc_cat_item Catalog Item
sc_cat_item_wizard Wizard Launcher sc_cat_item Catalog Item
sc_request Request task Task
sc_req_item Requested Item task Task
sc_task Catalog Task task Task
survey_question_new Question question Question
sysapproval_group Group Approval task Task
sysauto_report Scheduled Email of Report sysauto Scheduled Job
sysauto_script Scheduled Script Extension sysauto Scheduled Job
sysauto_template Scheduled Entity Generation sysauto Scheduled Job
sysevent_email_action Email Notification sysrule Rule
sysevent_in_email_action Inbound Email Actions sysrule Rule
sysevent_script_action Script Action sysrule Rule
syslog_transaction Transaction Log Entry syslog Rule
sysrule_approvals Approval Rules sysrule Rule
sysrule_assignment Assignment Rules sysrule Rule
sysrule_escalate Service Level Agreement sysrule Rule
sysrule_escalate_am Inactivity Monitor sysrule_escalate Service Level Agreement
sysrule_view View Rule sysrule Rule
ticket Ticket task Task
var_dictionary Variables sys_dictionary Dictionary
v_field_editor Edit Field v_field_creator Create Field
v_table_editor Edit Table v_table_creator Create Table
v_ws_creator Create Web Service v_table_creator Create Table
v_ws_editor Edit Web Service v_ws_creator Create Web Service
v_ws_field_creator Create Web Service Field v_field_creator Create Field
v_ws_field_editor Edit Web Service Field v_field_editor Edit Field
wf_activity_variable Activity Variables var_dictionary Variables
wf_log Workflow Log Entry syslog Log Entry
wf_variable Workflow SC Variable item_option_new Variable
wf_workflow_schedule Workflow Schedule sysauto_script Scheduled Script Execution