DB-design question

[webpoet]

I´m creating a small application and when planning the database I´m finding myself having a table with about 30 columns. Logically there is no point in separating them at all but I recall having read somewhere that one should never have that many columns in a single table. I can´t remember the motivation tho.

Finding natural groups in the columns to separate them neatly wouldn´t be a problem and maybe speed up the update process slightly (?) but each time I would do select-queries I would have to join the different tables.

So, my question is: Is it really bad to have alot of columns in one table even if they belong there, and in that case why ?

[tomhath]

If you really have 30 distinct pieces of information you need to keep, then there's nothing wrong with putting them all in one big row.

On the other hand, if you're repeating something several times, you have an array inside a row, and that's not good.

For example, if you need to keep 3 phone numbers for a person, you should have a child table with a phone number column and three rows of data, not a table that has three different columns all holding phone numbers.