Varchar vs Nvarchar: Complete Database Guide

The primary difference between varchar and nvarchar is that nvarchar stores Unicode characters using 2 bytes per character while varchar stores non-Unicode characters using 1 byte per character. Nvarchar supports a much wider range of characters including multibyte characters from various languages, emojis, and special symbols, whereas varchar is limited to the character set defined by the database’s collation. Beyond storage considerations, varchar offers performance advantages for non-Unicode data and avoids conversion overhead, though nvarchar provides consistent Unicode support across all modern systems and eliminates encoding conversion issues.

Contents

• Core Differences Between Varchar and Nvarchar
• Character Encoding and Storage Mechanics
• Performance Considerations
• Practical Usage Guidelines
• Modern Database Support
• When to Choose Each Data Type

Core Differences Between Varchar and Nvarchar

The fundamental distinction between varchar and nvarchar lies in their character encoding and storage approach:

• Varchar: Stores non-Unicode string data using 1 byte per character
• Nvarchar: Stores Unicode string data using 2 bytes per character (stored as byte-pairs)

This encoding difference directly impacts which characters each data type can support. As Microsoft’s documentation explains, “nvarchar stores Unicode characters and varchar stores non-Unicode characters” source.

The character range support differs dramatically:

• Varchar: Limited to the character set defined by the database’s collation/code page (typically 256 characters)
• Nvarchar: Supports full Unicode range (0-1,114,111 characters), including multibyte characters

“Each nvarchar character uses 2 bytes of storage and can represent 65,536 different characters. If you need to support text like arabic, chinese, or emojis, use nvarchar.” source

Character Encoding and Storage Mechanics

Storage Size Implications

The storage difference between these data types is significant:

This means that for the same logical number of characters, nvarchar columns consume twice as much storage space as varchar columns. According to Microsoft Learn, “varchar only uses 1 byte” while “nvarchar stores data at 2 bytes per character.”

Row Size Limitations

The storage differences have practical implications for database design:

• Varchar: Can store up to 8,000 characters per column
• Nvarchar: Limited to 4,000 characters per column due to the 2-byte-per-character storage

This creates important row size considerations:

• SQL Server has an 8,060 byte row limit
• Nvarchar columns can push data off-row sooner than varchar columns
• Index key limitations: nvarchar columns may hit the 900-byte index key limit faster

As noted in the Database Administrators Stack Exchange, “You may have to use shorter nvarchar columns to keep rows within the 8060 byte row limit/8000 byte character column limit.”

Code Page vs Unicode Support

The character encoding support represents the most critical distinction:

• Varchar: Tied to the database’s collation and code page

  • Cannot reliably store characters outside the defined code page
  • Risk of data corruption or replacement with ‘?’ characters when encountering unsupported characters
  • Limited to ASCII and extended character sets

• Nvarchar: Full Unicode support

  • Can store characters from any language
  • Supports emojis, mathematical symbols, and special characters
  • Consistent behavior across different systems and collations

“Varchar data type can store non-Unicode string data. Varchar stores data at 1 byte per character. Varchar supports up to 8000 characters. Nvarchar data type can store Unicode string data. Nvarchar stores data at 2 bytes per character.” source

Performance Considerations

Storage and Memory Impact

The doubled storage requirements of nvarchar have measurable performance implications:

• Memory Usage: Nvarchar columns consume twice as much memory as varchar columns for the same data
• Disk I/O: Larger storage requirements mean more disk space usage and potentially more I/O operations
• Cache Efficiency: Smaller varchar data fits better in database cache, improving performance

According to SQLServerCentral Forums, “Each character of an nvarchar column requires 2 bytes of storage whereas a varchar column requires 1 byte per character. Potentially, varchar will be quicker but that may well mean that you cannot store the data that you need.”

Conversion Overhead

Type conversions between varchar and nvarchar create performance bottlenecks:

• Implicit Conversions: When joining or comparing varchar and nvarchar columns, SQL Server must convert data types
• Explicit Conversions: Using the N prefix for string literals in nvarchar columns
• Dynamic SQL: Converting between types for stored procedures like sp_executesql

The Stack Overflow discussion notes that “JOIN-ing a VARCHAR to NVARCHAR has a considerable performance hit” and recommends “doing all string manipulations (concatenation, replacement etc.) in VARCHAR then converting the end result to NVARCHAR” when performance is critical.

Execution Speed Differences

For non-Unicode data operations, varchar generally outperforms nvarchar:

-- VARCHAR operations are typically faster for non-Unicode data
SELECT * FROM users WHERE username = 'testuser';  -- Faster with VARCHAR

-- NVARCHAR requires more processing due to Unicode handling
SELECT * FROM users WHERE username = N'testuser'; -- Slower with NVARCHAR

As The DBA Hub summarizes: “nVARCHAR provides full Unicode support at the cost of fixed storage and slightly slower performance, while VARCHAR offers variable storage and faster execution for non-Unicode data.”

Practical Usage Guidelines

When to Use Varchar

Choose varchar when:

1. Storing English-only text: Names, addresses, and basic alphanumeric data
2. Performance-critical applications: High-volume transaction systems
3. Storage-constrained environments: Where disk space is limited
4. Legacy system compatibility: Working with older systems that don’t support Unicode

As DesignGurus.io recommends: “For columns that store primarily non-Unicode data, prefer varchar to save space and potentially improve performance.”

When to Use Nvarchar

Choose nvarchar when:

1. International applications: Supporting multiple languages
2. Modern web applications: Handling user-generated content including emojis
3. Future-proofing: When data needs might expand beyond current character sets
4. Cross-platform compatibility: Ensuring consistent behavior across different systems

“If you need to support text like arabic, chinese, or emojis, use nvarchar. If you only expect alpha numeric and want storage benefits, varchar is better.” source

Best Practices for Data Type Selection

1. Never mix types in the same schema: Choose one consistently for related data
2. Use appropriate sizes: Avoid unnecessarily large varchar/nvarchar columns
3. Consider the N prefix: Always use N prefix for Unicode string literals
4. Plan for future growth: Consider Unicode support even if not currently needed

The Microsoft Q&A emphasizes: “Using the N prefix is great advice, but it’s mainly to avoid data loss (when Unicode chars not available in the code page associated with the current database’s default collation get converted to either ? or a “best fit” mapping of something similar).”

Modern Database Support

SQL Server 2019 and UTF-8 Support

A significant development in recent years is SQL Server 2019’s support for UTF-8 encoding with varchar columns:

• SQL Server 2019+: Varchar columns can now store UTF-8 encoded Unicode characters
• Reduced storage: UTF-8 uses variable-length encoding (1-4 bytes per character)
• Backward compatibility: Maintains compatibility with existing varchar usage

As noted in a Stack Overflow discussion: “Since SQL Server 2019 varchar columns support UTF-8 encoding. Thus, from now on, the difference is size. In a database system that translates to difference in speed.”

Cross-Database System Considerations

Different database systems handle varchar and nvarchar differently:

• MySQL: Uses VARCHAR with character sets instead of separate NVARCHAR type
• PostgreSQL: Uses TEXT with encoding specifications
• Oracle: Uses VARCHAR2 and NVARCHAR2 with similar distinctions

Understanding these differences is important for cross-database compatibility and migration scenarios.

When to Choose Each Data Type

Decision Framework for Varchar vs Nvarchar

Use this decision tree to choose the appropriate data type:

Does your data need to support:
├── Non-English characters, emojis, or special symbols?
│   └── YES → Use NVARCHAR
│   └── NO → Continue to next question
├── Performance-critical operations with high volume?
│   └── YES → Use VARCHAR (if Unicode not needed)
│   └── NO → Continue to next question
├── Future expansion beyond current character requirements?
│   └── YES → Use NVARCHAR
│   └── NO → Use VARCHAR
└── Legacy system compatibility requirements?
    └── YES → Use VARCHAR (if legacy system doesn't support Unicode)
    └── NO → Use NVARCHAR for modern applications

Storage vs Performance Trade-offs

The choice ultimately involves balancing storage efficiency against character support:

As the Database Administrators Stack Exchange discussion concludes: “Some experts recommends nvarchar always because: since all modern operating systems and development platforms use Unicode internally, using nvarchar rather than varchar, will avoid encoding conversions every time you read from or write to the database.”

Conclusion

The differences between varchar and nvarchar extend far beyond simple storage considerations. While nvarchar’s primary advantage is its support for multibyte characters and full Unicode compatibility, varchar offers significant performance benefits for non-Unicode data. The practical advantages of using varchar include:

1. Performance benefits: Faster execution for non-Unicode operations due to smaller storage footprint
2. Memory efficiency: Lower memory usage for the same amount of data
3. Disk space savings: 50% reduction in storage requirements
4. Avoidance of conversion overhead: Eliminates implicit conversions between data types
5. Better cache utilization: Smaller data fits better in database cache

However, these advantages come with the limitation of character set restrictions. Modern applications with international users, social media features, or future expansion needs should strongly consider nvarchar despite the storage and performance costs. SQL Server 2019’s UTF-8 support for varchar has blurred some distinctions, but nvarchar remains the safer choice for comprehensive Unicode support.

The decision ultimately depends on your specific application requirements, user base, performance needs, and future growth plans. For new applications, the trend is toward nvarchar for its consistency and future-proofing, while varchar remains valuable for performance-critical, English-only systems.

Sources

1. What is the difference between varchar and nvarchar? - Stack Overflow
2. varchar vs nvarchar - Microsoft Q&A
3. char and varchar (Transact-SQL) - SQL Server Documentation
4. nchar and nvarchar (Transact-SQL) - SQL Server Documentation
5. Write differences between varchar and nvarchar - Database Administrators Stack Exchange
6. What is the difference between VARCHAR and NVARCHAR - Reddit
7. SQL Server differences of char, nchar, varchar and nvarchar data types - MSSQLTips
8. Difference between Varchar and Nvarchar in SQL - TSQL.info
9. Understanding the Difference Between nVARCHAR and VARCHAR - The DBA Hub
10. varchar vs. nvarchar - performance? - SQLServerCentral Forums