String field length in Postgres SQL

Question

I have a string filed in an SQL database, representing a url. Some url\'s are short, and some very long. I don\'t really know waht\'s the longest URL I might encounter, so t

Answer 1

Usually database storage engines can do many thing you don't expect. But basically, there are two kinds of text fields, that give a hint what will go on internally.

char and varchar. Char will give you a fixed field column and depending on the options in the sql session, you may receive space filled strings or not. Varchar is for text fields up to a certain maximum length.

Varchar fields can be stored as a pointer outside the block, so that the block keeps a predictable size on queries - but that is an implementation detail and may vary from db to db.