Figure 2.1 missing employee_id field in zoo table

[weinberg]

The relationship between zoos and employees is missing from the tables in Figure 2.1. The line (and the descriptive text) says that a zoo has 0 or more employees and an employee has 0 or more zoos but there is no foreign key in either zoo or employee table.

Seems like you need +employee_id in the zoo table or +zoo_id in the employee table (or both?).

Actually, I just realized you are using this notation to represent a join table. Sorry - this can be ignored. Thanks for the good read.