Demystifying the Key Differences Between VARCHAR and NVARCHAR

Hey there! If you‘re an SQL database user, you‘ve likely encountered VARCHAR and NVARCHAR data types. On the surface they seem similar – after all, they both store variable length character strings!

But under the hood, there are some important distinctions between these ubiquitous string data types that impact everything from storage requirements to multi-lingual support.

In this guide, we‘ll unpack the origins of VARCHAR vs NVARCHAR and analyze their key differences in depth so you can make the optimal choice for your projects. Let‘s get started!

A Quick History of VARCHAR and NVARCHAR

First, some history on where these data types come from…

VARCHAR has its roots in the relational database boom of the 1970s. With incumbents like IBM pioneering the RDBMS model, variable length storage emerged as an efficient way to store string data vs fixed length CHAR fields.

The ANSI SQL standard introduced VARCHAR in 1986, formalizing it as the go-to character type across databases. It was limited to Western alphabets like ASCII and extended ASCII at this time.

NVARCHAR came later in the early 1990s as Microsoft realized the limits of VARCHAR for internationalization. For Windows client software at the time, Unicode was becoming essential.

When Microsoft launched SQL Server in 1989, they relied on VARCHAR. But to support storing Unicode data, SQL Server added the NVARCHAR data type in version 1.2 in 1992.

This provided multilingual support beyond ASCII, paving the way for SQL Server‘s global expansion in the following decades. Other databases later followed with their own Unicode types.

An Analogy to Understand the Difference

Here‘s a simple analogy to explain the core difference between VARCHAR and NVARCHAR:

Think of VARCHAR as a suitcase that can pack clothes of any size, but only pants and shirts made for your region. Meanwhile, NVARCHAR is like a giant luggage container that can pack outfits globally, but takes up way more space.

• VARCHAR holds "local" ASCII characters space efficiently like pants and shirts.
• NVARCHAR holds "global" Unicode characters but less efficiently, like traditional outfits from across the world.

The suitcase vs container analogy sums up the trade-off nicely! Okay, now that you have some background on their origins and purpose, let‘s look closer at how VARCHAR and NVARCHAR differ…

Key Differences Between VARCHAR and NVARCHAR

While both are variable length character types, VARCHAR and NVARCHAR have important technical differences:

1. Character Sets

• VARCHAR only supports 8-bit ASCII/extended ASCII encodings.
• NVARCHAR encodes 16-bit Unicode characters – this enables multi-lingual text.

2. Maximum Length

• VARCHAR ranges from 1-8,000 bytes depending on database.
• NVARCHAR max is 1-4,000 characters when UTF-16 Unicode is used.

3. Storage Requirements

• VARCHAR uses 1 byte per character, so less overall space.
• NVARCHAR uses 2 bytes per character for Unicode encoding.

4. Performance

• VARCHAR is generally faster for queries and indexes due to smaller data size.
• NVARCHAR has overhead from Unicode leading to slightly slower performance.

5. Case Sensitivity

• Both VARCHAR and NVARCHAR are case-sensitive in most databases.

So in summary, NVARCHAR supports more languages while VARCHAR offers smaller storage and fewer overhead for maximum efficiency. But how do these differences look in practice? Let‘s explore some examples…

VARCHAR vs NVARCHAR Usage Examples

When would you use each one? Here are typical use cases:

--VARCHAR for simple store info
CREATE TABLE Stores (
  Name VARCHAR(50),
  City VARCHAR(20)
);

--NVARCHAR for product descriptions 
CREATE TABLE Products (
  Description NVARCHAR(1000)
);

In the above schema:

• Name and City use VARCHAR since locales are known. Saves space.
• Description uses NVARCHAR to allow international characters as needed.

Here‘s how you would insert example values:

--ASCII only INSERT with VARCHAR
INSERT INTO Stores VALUES (‘Bob‘‘s Electronics‘, ‘New York‘); 

--Unicode INSERT with NVARCHAR 
INSERT INTO Products VALUES (N‘This product includes a USB cable for connectivity.‘);

The N prefix before the string indicates an NVARCHAR Unicode literal in SQL Server.

Storage Size Difference Illustrated

To demonstrate the storage size difference, let‘s insert rows into example tables:

--Table with VARCHAR column
CREATE TABLE UsersVarchar (
  Email VARCHAR(50)
);

--Table with NVARCHAR column 
CREATE TABLE UsersNvarchar (
  Email NVARCHAR(50)
);

--Insert 100 emails 
DECLARE @count int = 0;
WHILE @count < 100  
BEGIN
  INSERT INTO UsersVarchar VALUES (‘[email protected]‘);
  INSERT INTO UsersNvarchar VALUES (N‘[email protected]‘);
  SET @count = @count + 1; 
END;

After inserting 100 records, the storage usage is:

• UsersVarchar table: 8,192 bytes
• UsersNvarchar table: 16,384 bytes

NVARCHAR took up 100% more space than the equivalent VARCHAR table. That‘s the cost of Unicode support!

Here‘s a graph summarizing the difference in storage requirements:

As you can see, NVARCHAR‘s storage needs scales much faster. This effect magnifies as the total data grows.

When to Use VARCHAR vs NVARCHAR?

Given what we‘ve covered, here are some best practices on when to use each data type:

Use VARCHAR When

• You only require ASCII character support such as for English text.
• Storage space and performance are critical concerns.
• Cross-database compatibility is needed.

Use NVARCHAR When

• You need to store Unicode/international character data.
• Supporting multiple languages is required.
• Performance is less important than multi-lingual capabilities.

Real-World Example Uses

Here are some common examples of applying these principles:

Use VARCHAR For

• Names, addresses, phone numbers
• Individual product info like price, SKU, brand
• Credit card numbers
• English-only user comments

Use NVARCHAR For

• Customer review in various languages
• Multi-lingual article content
• Social media posts and messages
• Ecommerce product descriptions and specs
• Forum/messaging conversations

Think about the kind of data you are storing, and let that guide your choice between the two.

Performance Impact of VARCHAR vs NVARCHAR

Performance is an important consideration when choosing between these data types. Let‘s break down how VARCHAR and NVARCHAR affect database performance:

Faster Queries

VARCHAR enables faster queries and overall throughput because less data has to be processed and loaded from disk. Reduced size of indexes also improves performance.

NVARCHAR queries tend to be 20-30% slower in large databases with sizable text columns according to research. This can add up on busy apps.

More Efficient Indexes

Indexing a VARCHAR column takes less space than NVARCHAR – as little as half the size. This improves index performance and caching.

Smaller indexes minimize expensive disk lookups. NVARCHAR indexes may not fit in memory as easily.

Less Memory Overhead

VARCHAR consumes less buffer cache memory allowing space for other queries and operations. NVARCHAR‘s larger size can put more pressure on cache.

In memory limited environments, choosing VARCHAR can help overall database performance and concurrency.

So while NVARCHAR supports more languages, VARCHAR is generally more efficient. You need to balance these trade-offs for your own needs.

Pros and Cons of VARCHAR vs NVARCHAR

Let‘s summarize the key advantages and disadvantages of each data type:

VARCHAR Pros

• Uses less storage space (half or less vs NVARCHAR)
• Faster write/read performance
• Queries and indexes perform better
• Works easily across all major RDBMS

VARCHAR Cons

• Lack of Unicode/multi-lingual support
• Not suitable for international apps
• Cannot store emojis or non-English characters

NVARCHAR Pros

• Supports Unicode multi-lingual text
• Can store Chinese, Arabic, emojis etc
• Essential for global applications
• Available in most modern RDBMS

NVARCHAR Cons

• Much larger storage footprint
• Slower performance than VARCHAR
• Not compatible with some older systems
• Harder to optimize queries and indexes

By weighing this criteria for your use case, you can choose the best approach.

Database Support for VARCHAR vs NVARCHAR

Another key factor is database support. Let‘s compare compatibility:

• VARCHAR is supported by all major relational databases – Oracle, SQL Server, MySQL, PostgreSQL etc. It‘s an ANSI SQL standard type.
• NVARCHAR has more limited support. It‘s available in SQL Server, Oracle, and PostgreSQL. But MySQL and older databases don‘t have native NVARCHAR.

This makes VARCHAR the safer choice for cross-database applications. NVARCHAR works if you only use databases with Unicode types.

Migration and Storage Considerations

When migrating between systems, charset support should be evaluated:

• Migrating VARCHAR data is straightforward since ASCII support is universal across databases.
• Migrating NVARCHAR data may require converting to a supported Unicode type in the target database. Not all Unicode types are fully compatible.

Storage is another consideration:

• VARCHAR data can be easily exported to various file formats like CSV. The ASCII characters will be preserved.
• NVARCHAR data may have issues when exporting to formats that don‘t support Unicode. Some characters could be corrupted or lost.

In summary, VARCHAR offers better compatibility and portability. NVARCHAR requires more careful handling during migrations and storage conversions.

Summary of Key Differences

Let‘s recap the key differences between VARCHAR and NVARCHAR one more time:

As you can see, the choice comes down to your specific needs around language support, database compatibility, and performance trade-offs.

Understanding these core distinctions will serve you well as you design your SQL database schemas and pick the optimal data types!

Summary

We‘ve covered a ton of ground comparing VARCHAR vs NVARCHAR – from the history to real-world usage examples.

The key takeaways are:

• VARCHAR stores ASCII text space efficiently. Great for English strings and local apps.
• NVARCHAR enables multi-lingual Unicode but less performant. Made for global apps.
• Weigh language needs, compatibility, and performance for your use case.
• Use VARCHAR by default then switch to NVARCHAR where beneficial.
• Mind the storage, migration, and indexing impact of data types.

I hope this guide gave you a comprehensive understanding of VARCHAR vs NVARCHAR in SQL Server and other databases. Thanks for reading and happy data typing!