One-to-many relationships are one type of parent-child relationship. They consist of one parent record, that is linked to many child records. This linkage is done via database table keys.
As we briefly mentioned in a previous chapter, records have a primary key (PK), and a foreign key (FK) column. The PK in ServiceNow is the Sys ID. Every record in ServiceNow has a Sys ID that is unique within the entire database. An example of an FK column, is any column which is meant to hold the PK of another record. These fields are Reference fields in ServiceNow. The Incident [incident] table for example, contains an FK column with the label Assigned to, and an actual column name of assigned_to. This is a Reference field that points to the User [sys_user] table, and contains the PK (Sys ID) of one of the records in that table.
