Question

I have two tables.

User_types

• (1)individual
• (2)business
• (3)student

Relationship_cat

• cat_id
• cat_name
• user_id
• user_type

First with Relationship_cat, i want an entry to look like this

cat_id(1), cat_name(interests) ,user_id(ANy user), user_type(only 1 and 3)
cat_id(2), cat_name(news) ,user_id(ANy user), user_type(only 2 and 3)
etc

With user_type i believe i could set it to 0 as default so it’s not constrained to any user. How do I go about the "relationship_cat > user_type" case? Do I use a comma separated list of values? Is it efficient? And what if there are many User_types entries increase?

Answer 1

You should use a many-to-many join table. So your schema might look like this:

user_types

• user_type_id
• user_type_value

categories

• cat_id
• cat_name

categories_to_user_types

• cat_id
• user_type_id

Any time you may think about using comma-separated values like you mentioned, this should be a sign to you to further normalize your tables. What I have shown is typically the best way to express a many-to-many relationship between tables.