Difference between different string types in SQL Server?

Question

What is the difference between char, nchar, ntext, nvarchar, text and varchar in SQL?

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Answer 1

The n prefix simply means Unicode. They "n" types work similarly to the plain versions except they work with Unicode text.

char is a fixed length field. Thus char(10) filled with "Yes" will still take 10 bytes of storage.

varchar is a variable length field. char(10) filled with "Yes" will take 5 bytes of storage (there is a 2 byte overhead for using var data types).

char(n) holding string of length x. Storage = n bytes. varchar(n) holding string of length x. Storage = x+2 bytes.

vchar and nvarchar are similar except it is 2 bytes per character.

Generally speaking you should only use char & char (over varchar & nvarchar) when working with fixed or semi-fixed strings. A good example would be a product_code or user_type which is always n characters long.

You shouldn't use text (or ntext) as it has been deprecated. varchar(max) & nvarchar(max) provides the same functionality.