Foreign keys
Recall that foreign keys reference another row in the database via a unique ID. Values in a foreign key column are restricted to values in the referenced column OR NULL
.
Using what you know about foreign keys, why can't the tag
column in the tag_type
table be a foreign key that references the tag
column in the stackoverflow
table?
Remember, you can reference the slides using the icon in the upper right of the screen to review the requirements for a foreign key.
This exercise is part of the course
Exploratory Data Analysis in SQL
Hands-on interactive exercise
Turn theory into action with one of our interactive exercises
