Table Compare (found under DataSync > Tools) allows you to compare a table on your ServiceNow instance with the table in another database or another ServiceNow instance. By comparing two tables, you can see each table's record count as well as a list of record discrepancies by sys_id between the two tables that you are comparing (i.e. which records exist in one table and not in the other).
NOTE: Table Compare will NOT check for the most recent update of a record. It will only check for the existence of records.
ServiceNow to ServiceNow Table Compare
Learn how to run a table compare for two ServiceNow instances via DataSync for ServiceNow.
ServiceNow to Database Table Compare
Learn how to run a table compare for a ServiceNow instance and a database via DataSync for ServiceNow.