Difference Between VARCHAR and NVARCHAR

When designing databases, choosing the correct data type for storing text is essential for performance, storage efficiency, and internationalization. Two commonly used data types in SQL Server are VARCHAR and NVARCHAR. While they might appear similar, they serve different purposes and have key distinctions.

Difference Between VARCHAR and NVARCHAR in SQL

Getting Started

Understanding the difference between VARCHAR and NVARCHAR is critical for designing efficient and internationalized applications when working with databases. While both data types are used to store text, they differ in how they handle character encoding and storage, which can impact performance, storage space, and language support.

What is `VARCHAR`?

VARCHAR stands for Variable Character. It is a data type used to store non-Unicode character strings. That means it supports only characters defined in the server's code page, typically ASCII or another local character set.

Key Features:

Stores non-Unicode data.
Uses 1 byte per character (in most code pages).
Has a storage limit of up to 8,000 characters in SQL Server (or more using VARCHAR(MAX)).

Example:

DECLARE @name VARCHAR(50)
SET @name = 'John Smith'

What is NVARCHAR?

NVARCHAR stands for National Variable Character and is used to store Unicode character strings. Unicode supports a much wider range of characters, including those from languages such as Chinese, Arabic, Hebrew, and many others.

Key Features:

Stores Unicode data using UTF-16 encoding.
Uses 2 bytes per character.
Supports characters from virtually all languages.
Has a storage limit of up to 4,000 characters (or more using NVARCHAR(MAX)).

Example:

DECLARE @name NVARCHAR(50)
SET @name = N'李小龙'  -- Chinese characters

Note the N prefix before the string, which indicates a Unicode literal.

Key Points of `VARCHAR` VS `NVARCHAR`

Feature	`VARCHAR`	`NVARCHAR`
Character Support	Non-Unicode (ASCII only)	Unicode (supports all characters)
Storage	1 byte per character	2 bytes per character
Use Case	English or Western language text	Multilingual text, special symbols
Prefix	No special prefix needed	Requires an `N` prefix for literals
Example	`'Hello'`	`N'こんにちは'`
Performance	Slightly better due to less storage	Slightly slower due to more storage

When to Use `VARCHAR`

When your application only supports English or Western European languages.
When minimizing storage is critical and Unicode support is not needed.
For legacy applications where Unicode was not previously used.

Example Use Cases:

Email addresses
URLs
Alphanumeric IDs
Names in English

When to Use `NVARCHAR`

When supporting multiple languages (e.g., Chinese, Arabic, Hindi, etc.).
When storing special symbols or emojis.
For applications with international users or global reach.

Example Use Cases:

International user names
Product descriptions in multiple languages
Addresses that include non-Latin characters

Important Consideration

When comparing NVARCHAR and VARCHAR fields, be cautious:

-- This will fail to match if 'col' is NVARCHAR
WHERE col = 'somevalue'    -- Wrong: no N prefix
WHERE col = N'somevalue'   -- Correct: Unicode literal

Common Mistakes to Avoid

Storing Unicode in VARCHAR: If you insert Unicode data into a VARCHAR column without using the N prefix, the data will be lost or corrupted.
Overusing NVARCHAR: Using NVARCHAR everywhere can unnecessarily double your storage requirements, impacting performance and database size.

Summary

Choosing between VARCHAR and NVARCHAR depends on your application's language requirements and storage considerations. For English-only or single-language applications, VARCHAR can save space and improve performance. However, for applications that need to support international characters or multiple languages, NVARCHAR is the safer and more future-proof choice.

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Difference Between VARCHAR and NVARCHAR