Junction table question

Question

I have 3 Northwind tables, Employees, EmployeeTerritories, and Territories. I have a cross join table between Employees and Territories. I want to add a column to the cross join table. Each row will contain a 1 if the row employee has the row territory
and will contain a 0 otherwise. How do I do it?
Bill Swartz

Answer 1

>> I have 3 Northwind tables, Employees, Employee_Territories, and Territories. <<
Northwind is one of the worst sample schema in use. It has to show all of the features in T-SQL, so it is improperly written and it is full of ISO-11179 violations. Do not use it to learn RDBMS! For example, does that table model the set “Personnel” or the
single “Employee”, as you named it? 
>> I have a cross join table between Employees and Territories. <<
The term “junction table” is not RDBMS; it belong to one of the old Network Databases (I cannot remember which one). Even the use of the absurd “Employee_Territories” is the old Network convention of building the pointer structure from the names of the files
involved. 
There is no such thing as a “CROSS JOIN” table in RDBMS or Network Database. This is a relational join operator, not a table type! I think you mean a relationship table (that is where the R in RDBMS comes from).  
Look up 1:m (one to many), 1:1 (one to one) and n:m (many to many), cardinality, membership and the other terms that apply to relationships in RDBMS. You lack of DDL was doubly rude; we have no specs. I will guess each territory has one and only one employee
assigned to it (why not?). I will enforce this with DRI constraints. 
>> I want to add a column to the cross join [sic] table. Each row will contain a 1 if the row employee has the row territory and will contain a 0 otherwise. How do I do it? <<
BIT flags in RDBMS?? No, that was assembly language. This is worse than the network mindset. 
CREATE TABLE Territory_Assignments
(emp_id CHAR(10) NOT NULL UNIQUE  -- enforce 1:m
  REFERENCES Personnel(emp_id)
  ON UPDATE CASCADE
  ON DELETE CASCADE,
 territory_id CHAR(10) NOT NULL 
  REFERENCES Personnel(territory_id)
  ON UPDATE CASCADE
  ON DELETE CASCADE,
 PRIMARY KEY (emp_id, territory_id));
You lack basics and need to un-learn a lot. 
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