CHAR vs VARCHAR vs NCHAR vs NVARCHAR

CHAR, VARCHAR, NCHAR, and NVARCHAR in SQL Server

These data types store text. The main differences are:

1. Fixed-length vs variable-length

2. Unicode vs non-Unicode

1. CHAR(n)

Stores a fixed number of characters. SQL Server pads shorter values with trailing spaces.

DECLARE @Code CHAR(5) = 'AB';

Stored logically as:

'AB   '

Use it for consistently sized values:

GenderCode CHAR(1)
CountryCode CHAR(2)

2. VARCHAR(n)

Stores variable-length non-Unicode text, using only the space required for the value plus internal length information.

DECLARE @Name VARCHAR(50) = 'Syed';

Use it when values have different lengths and Unicode is unnecessary:

Email VARCHAR(200)
Url   VARCHAR(500)

3. NCHAR(n)

Stores fixed-length Unicode text. Shorter values are padded with trailing spaces.

DECLARE @Code NCHAR(5) = N'தமிழ்';

Use it for fixed-length codes containing international characters.

4. NVARCHAR(n)

Stores variable-length Unicode text and supports languages such as Tamil, Hindi, Arabic and Chinese.

DECLARE @Name NVARCHAR(100) = N'சையது';

Use it for multilingual data:

CustomerName NVARCHAR(100)
Address      NVARCHAR(500)

The N prefix marks a string literal as Unicode:

INSERT INTO Customers(Name)
VALUES (N'சையது');

Without N, Unicode characters can be converted incorrectly, depending on the database collation and encoding.

Storage difference

Traditionally:

• CHAR and VARCHAR use 1 byte per character for common single-byte code pages.

• NCHAR and NVARCHAR use UTF-16 and usually require 2 bytes per character.

However, exact storage depends on the character and collation. Supplementary Unicode characters may require more space, and VARCHAR can store Unicode when using a UTF-8-enabled collation.

Simple comparison

CREATE TABLE Employee
(
    CountryCode CHAR(2),          -- Fixed, non-Unicode
    Email       VARCHAR(200),     -- Variable, non-Unicode
    LanguageKey NCHAR(2),         -- Fixed, Unicode
    DisplayName NVARCHAR(100)     -- Variable, Unicode
);

Key interview points

• CHAR and NCHAR are fixed-length and pad values with spaces.

• VARCHAR and NVARCHAR are variable-length.

• Types beginning with N support Unicode using UTF-16.

• Use NVARCHAR when multilingual characters must be supported.

• Use the smallest sensible length instead of automatically using MAX.

• VARCHAR(MAX) supports approximately 2 GB of data.

• NVARCHAR(MAX) supports approximately 1 billion UTF-16 code units—about 2 GB.

• VARCHAR may support Unicode with a UTF-8 collation.

• Changing a column to Unicode can affect storage, index size and performance.

• Avoid deprecated TEXT and NTEXT; use VARCHAR(MAX) and NVARCHAR(MAX) instead.