Databases: Are "TEXT" fields less efficient than "varchar"?

Question

Is it less efficient to use TEXT than varchar in an SQL database?

If so why?

If not why would you not just always use TEXT?

I'm not targetting a specific database here but oracle is probably the most relevant, although I'm testing on MySQL for the time being as part of a proof of concept.

Answer 1

From Microsoft here

ntext, text, and image data types will be removed in a future version of Microsoft SQL Server. Avoid using these data types in new development work, and plan to modify applications that currently use them. Use nvarchar(max), varchar(max), and varbinary(max) instead.

When you use varchar(max) over text you can use it in the WHERE clause, because they work the same as their smaller counterparts, varchar,nvarchar and varbinary. Below is a small list of what should be used as opposed what was to be used:

• Use varchar(max) instead of text
• Use nvarchar(max) instead of ntext
• Use varbinary(max) instead of image

Answer 2

PostgreSQL documentation says:

Tip: There are no performance differences between these three types, apart from increased storage size when using the blank-padded type, and a few extra cycles to check the length when storing into a length-constrained column. While character(n) has performance advantages in some other database systems, it has no such advantages in PostgreSQL. In most situations text or character varying should be used instead.