Can a table have more than one relationship?
Creating a new table with 1-1 relationships is not a reasonable solution. You might need to do it sometimes, but there would typically be no reason to have two tables where the user id is the primary key. On the other hand, splitting the settings into a separate table with one row per user/setting combination might be a very good idea.
Which is better a single table or three table?
On the other hand, splitting the settings into a separate table with one row per user/setting combination might be a very good idea. This would be a three-table solution. One for users, one for all possible settings, and one for the junction table between them. The junction table can be quite useful.
Do you have to have two tables in a database?
You might need to do it sometimes, but there would typically be no reason to have two tables where the user id is the primary key. On the other hand, splitting the settings into a separate table with one row per user/setting combination might be a very good idea. This would be a three-table solution.
When to split a table into two or more?
You would normally split tables into two or more 1:1 related tables when the table gets very wide (i.e. has many columns). It is hard for programmers to have to deal with tables with too many columns. For big companies such tables can easily have more than 100 columns.
Why do you need a one to one relationship in SQL?
With separate tables you can grant different rights on the product’s main table and the product’s logistic table. So all in all, it is rather rare to see 1:1 relations, but they can give a clearer view on data and even help with performance issues and data access.
Can a user table be in more than one table?
The decision whether to hold data in only one table or more 1:1 related tables has nothing to do with this. You can decide to split a user table in one table for personal information like first and last name and another for his school, graduation and job.