I've read a lot from both camps in the surrogate vs. natural key debate. What I am struggling to understand, and what seems to be glossed over, especially in explaining how surrogate keys are more efficient, is how do referencing tables resolve a surrogate key?
Say, I am using an ORM in an application, and have a userID in an application object. now we want to insert into a SelectedTask table and a SubTask table that are defined as follows (ignore the awkwardness of the real word example):
CREATE TABLE SelectedTask(userID INT References User(userID)taskNumber INT,name TEXT ,jobSiteID INT References Site(jobSiteID),PRIMARY KEY (???));CREATE TABLE SubTask(assignee INT References User(assignee),subTaskID INT References Subtasks(subTaskID),timeAllowed INT,reportTo INT References Group(reportTo),-- how do we reference SelectedTask?);If we use a surrogate key for the SelectedTask table, how do we use that in the SubTask table? If we use natural keys, the primary key could simply be a compound primary key of userId and taskNumber, and we could insert into both at the same time assuming we have programmatically gathered all of the pieces.