Is a one column table good design? [closed]

Answer 1

In terms of relational algebra this would be a unary relation, meaning "this thing exists"

Yes, it's fine to have a table defining such a relation: for instance, to define a domain.

The values of such a table should be natural primary keys of course.

A lookup table of prime numbers is what comes to my mind first.

Answer 2

I would say in general, yes. Not sure why you need just one column. There are some exceptions to this that I have seen used effectively. It depends on what you're trying to achieve.

They are not really good design when you're thinking of the schema of the database, but really should only be used as utility tables.

I've seen numbers tables used effectively in the past.

Answer 3

Yes, it's certainly good design to design a table in such a way as to make it most efficient. "Bad RDBMS Design" is usually centered around inefficiency.

However, I have found that most cases of single column design could benefit from an additional column. For example, State Codes can typically have the Full State name spelled out in a second column. Or a blacklist can have notes associated. But, if your design really does not need that information, then it's perfectly ok to have the single column.

Answer 4

I've used them in the past. One client of mine wanted to auto block anyone trying to sign up with a phone number in this big list he had so it was just one big blacklist.

Answer 5

If there is a valid need for it, then I don't see a problem. Maybe you just want a list of possibilities to display for some reason and you want to be able to dynamically change it, but have no need to link it to another table.

Answer 6

The only use case I can conceive of is a table of words perhaps for a word game. You access the table just to verify that a string is a word: select word from words where word = ?. But there are far better data structures for holding a list of words than a relational database.

Otherwise, data in a database is usually placed in a database to take advantage of the relationships between various attributes of the data. If your data has no attributes beyond its value how will these relationship be developed?

So, while not illegal, in general you probably should not have a table with just one column.