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.
- 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)).
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.
- 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)).
DECLARE @name NVARCHAR(50)
SET @name = N'李小龙' -- Chinese characters
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.
- 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.
- International user names
- Product descriptions in multiple languages
- Addresses that include non-Latin characters
Important Consideration
When comparingNVARCHAR 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 aVARCHARcolumn without using the N prefix, the data will be lost or corrupted. - Overusing
NVARCHAR: UsingNVARCHAReverywhere 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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