Database Performace - 1:1 relationship or merge the table? [closed]

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Based on performance, would it be better if two tables with 1:1 relationship has their column all merged into single table?

For example I have Users and Admins table. Admin shares all columns from Users but has its own specific columns like permission

so do I design the database like this (version A):

USERS         ADMINS
- id          - id
- username    - user_id
- password    - permission
- ...         - ...

or like this (version B)

USERS
- id
- username
- password
- permission (left empty when it's normal user)

Version A is cleaner but does version B is much faster? Which approach is more common?

Thanks

Answer 1

Cleaner solution should be given preference over faster hacks. However, in your case Admins seem to be only a role of the Users, not a separate entity. Merge the tables when as it is only a role that can be indicated by a column in the table. Use another table only when it is a separate entity.

So, in your case it should be "version B".

Answer 2

In this case there is no need for another entity 'table' for Admins, Just add attribute 'Admin Permission' in USERS entity so Version B is the right one here.