Why we limit length of columns values in MYSQL

Question

When we creating database for our application, We limited lengths of database columns.

example -

1. String (200)
2. int (5)

etc

Is there any effect on Speed or some effect?

Answer 1

First of all, one does not limit the length of a "database". Instead, one does limit the size of columns of tables in a database.

Why do we do this, you ask?

1. We don't want to waste any space for data that's never going to use it (that's what the varchar, varbinary and the like are for).
2. It's a best practice because it forces you to think of your data structure BEFORE you actually use it.
3. The less data there is the faster the processing of the application (that's a tautology).
4. It makes it easier to validate your data if you know exactely how much space it is allowed to take.
5. Full text indexes gain greatly when limited in size