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SQL Server Hosting - HostForLIFE :: Knowing SQL Server's VARCHAR and NVARCHAR variables

April 23, 2024 08:23 by author

Peter

In the realm of database management, understanding the nuances of data types is crucial for optimizing performance, storage and ensuring data integrity. When it comes to storing textual data, SQL Server offers a variety of data types, two of which are VARCHAR and NVARCHAR. While both are used for storing character data, they have significant differences that impact storage, indexing, and manipulation. In this comprehensive guide, we delve into the intricacies of VARCHAR and NVARCHAR in SQL Server, exploring their features, use cases, and performance implications.

VARCHAR
VARCHAR, short for Variable Character, is a data type used to store non-Unicode string data of variable length in SQL Server. It allocates storage only for the actual length of the data plus two bytes. The maximum storage size for VARCHAR is 8,000 bytes.
NVARCHAR

NVARCHAR, short for National Variable Character, is used to store Unicode string data of variable length. Unlike VARCHAR, NVARCHAR stores Unicode characters, allowing it to support multiple languages and character sets. It also allocates storage only for the actual length of the data plus two bytes. The maximum storage size for NVARCHAR is also 8,000 bytes.

What Sets VARCHAR and NVARCHAR Apart

Encoding of Characters

VARCHAR uses the underlying operating system's default code page, usually ANSI or ASCII, to store data in the database.
NVARCHAR uses the UTF-16 encoding technique to store Unicode data in the database. This makes it possible for NVARCHAR to support a large character set from multiple languages.

Size of Storage

For non-Unicode characters, VARCHAR uses one byte per character.
For Unicode characters, NVARCHAR takes two bytes each character.
For the same amount of text data, NVARCHAR takes more storage space than VARCHAR because of the Unicode encoding.

Data Range

Data in languages like English, Spanish, or French that do not require Unicode support can be stored using VARCHAR.
When working with multilingual applications or when the data may contain characters from several languages, NVARCHAR is crucial.

Performance-Related Issues

VARCHAR can provide marginally better performance in terms of storage and retrieval due to the smaller storage size, particularly when working with huge volumes of data.
NVARCHAR has a performance overhead because of its Unicode encoding and greater storage capacity. Nonetheless, on contemporary systems, this overhead is frequently insignificant, and in most situations, the advantages of Unicode support exceed the performance concerns.

Example 1. Storing English Text
Consider a scenario where you need to store the names of employees in a database table. Since the names are in English and do not require Unicode support, VARCHAR would be the appropriate choice.

CREATE TABLE dbo.Employees (
EmployeeID INT PRIMARY KEY,
FirstName VARCHAR(50),
LastName VARCHAR(50) );

In this example, we define the FirstName and LastName columns as VARCHAR data types with a maximum length of 50 characters each.

Example 2. Storing Multilingual Text
Now, suppose you're working on an international e-commerce platform that caters to customers from various countries, each with its own languages and character sets. In this case, using NVARCHAR would be necessary to support the diversity of languages.
CREATE TABLE dbo.Products (
ProductID INT PRIMARY KEY,
ProductName NVARCHAR(100),
Description NVARCHAR(MAX) );

Here, we define the ProductName and Description columns as NVARCHAR data types. The ProductName column stores the name of the product, while the Description column stores a detailed description. Using NVARCHAR ensures that the database can accommodate text in any language, facilitating a seamless user experience for customers worldwide.

Conclusion
VARCHAR and NVARCHAR are essential data types in SQL Server for storing character data. While VARCHAR is suitable for non-Unicode text and offers slightly better performance in terms of storage and retrieval, NVARCHAR is necessary when dealing with multilingual applications or when Unicode support is required. Understanding the differences between these data types is crucial for designing efficient database schemas and optimizing performance in SQL Server environments. By choosing the appropriate data type based on the nature of the data and the requirements of the application, developers can ensure data integrity, performance, and compatibility across different languages and character sets.

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