SQL Server nvarchar vs varchar – Which One Should Dev Use?

Greetings, Dev! Are you experiencing confusion in choosing between nvarchar and varchar when creating tables in SQL Server? This is a common dilemma among developers. But don’t worry, we will explore the differences and similarities between these data types to help you decide which one to use. Let’s begin!

Difference Between nvarchar and varchar Data Types

The nvarchar and varchar data types are used to store string data in SQL Server. The major difference between these two is the way they store data.

Storage

The varchar data type stores characters in a fixed length manner where the length of the string is interpreted as the number of bytes in the string. This means that the number of characters that can be stored in varchar columns is limited by the number of bytes the column can hold. The nvarchar data type, on the other hand, stores Unicode characters in a variable-length manner, where the size of the column indicates the maximum number of characters it can hold. This means that nvarchar columns can store more characters than varchar columns with the same storage size.

Performance

The performance of the two data types is different when it comes to data access and manipulation. Since nvarchar stores variable length data, it requires more memory than varchar, which uses a fixed length storage mechanism. This means that nvarchar can take up more disk space and memory than varchar. However, when it comes to manipulating data, nvarchar is faster than varchar, especially when dealing with string concatenation and comparison operations.

Collation

The collation setting determines how SQL Server compares and sorts character data. nvarchar data types use the Unicode collation, which is case-insensitive and accent-insensitive. varchar, on the other hand, uses collations based on the code page, which can be either case-sensitive or case-insensitive, depending on the setting.

When to Use nvarchar

The nvarchar data type is ideal for storing string data that involves multiple languages or when the application requires support for non-ASCII characters such as Chinese or Japanese. It is also ideal when dealing with data that requires different collations. For example, a multilingual website, where each page could be in a different language, would require the use of nvarchar data types.

Example

Column Name	Data Type	Maximum Characters
FirstName	nvarchar	50
LastName	nvarchar	50
Email	nvarchar	100

When to Use varchar

The varchar data type is ideal for storing string data that uses a single language, especially if the application only supports ASCII characters. It is also ideal when dealing with data that requires a consistent collation setting. For example, a database that stores English-only data would benefit from using varchar data types.

Example

Column Name	Data Type	Maximum Characters
ProductCode	varchar	10
ProductName	varchar	50
ProductDescription	varchar	255

FAQs

What is the difference between varchar and nvarchar?

The primary difference between the two is the way they store data. Varchar uses a fixed length storage mechanism, while nvarchar uses a variable length storage mechanism. Varchar stores characters in a fixed length manner where the length of the string is interpreted as the number of bytes in the string. Nvarchar stores Unicode characters in a variable-length manner, where the size of the column indicates the maximum number of characters it can hold.

Which is faster, varchar or nvarchar?

The performance of the two data types is different when it comes to data access and manipulation. Since nvarchar stores variable length data, it requires more memory than varchar, which uses a fixed length storage mechanism. However, when it comes to manipulating data, nvarchar is faster than varchar, especially when dealing with string concatenation and comparison operations.

When should I use nvarchar?

The nvarchar data type is ideal for storing string data that involves multiple languages or when the application requires support for non-ASCII characters such as Chinese or Japanese. It is also ideal when dealing with data that requires different collations.

When should I use varchar?

The varchar data type is ideal for storing string data that uses a single language, especially if the application only supports ASCII characters. It is also ideal when dealing with data that requires a consistent collation setting.

Can I convert a varchar column to nvarchar?

Yes, you can convert a varchar column to nvarchar using the ALTER TABLE statement. However, this process can be time-consuming and may require additional disk space and memory.

What is the difference between case-sensitive and case-insensitive collation?

Case-sensitive collation takes into account the case of each letter when comparing or sorting character data. This means that ‘A’ is not equal to ‘a’. Case-insensitive collation, on the other hand, ignores the case of each letter when comparing or sorting character data. This means that ‘A’ is equal to ‘a’.

Conclusion

Choosing between nvarchar and varchar data types depends on the specific needs of your application. When dealing with multi-language data, nvarchar is the ideal option. On the other hand, varchar is ideal for single-language data. In summary, take into account the performance, storage, and collation settings of both data types when making your decision.