Adventures in Machine Learning

Mastering the SQL Server NVARCHAR Data Type

SQL Server is a popular relational database management system that is widely used for storing and manipulating large amounts of data. One of the most commonly used data types in SQL Server is NVARCHAR, which is used to store variable-length Unicode character strings.

In this article, we will explore the different aspects of SQL Server NVARCHAR data type, including its syntax, column declaration, and the differences between VARCHAR and NVARCHAR data types. We will also delve into different examples of using NVARCHAR, including creating a new table with NVARCHAR columns, inserting data into NVARCHAR columns, and error handling when inserting data greater than the defined string length.

Syntax of NVARCHAR

NVARCHAR is a primary keyword in SQL Server, and its syntax consists of the keyword followed by the length of the string in parentheses. For example, NVARCHAR(50) indicates that the string stored in this column can have a maximum length of 50 characters.

NVARCHAR Column Declaration

NVARCHAR columns are declared in SQL Server using the keyword NVARCHAR followed by the maximum length of characters the string can have in parentheses. An example of declaring an NVARCHAR column is shown below:

CREATE TABLE Employee

(

ID INT PRIMARY KEY IDENTITY,

FirstName NVARCHAR(50),

LastName NVARCHAR(50),

Email NVARCHAR(100)

)

In this example, the Employee table has three NVARCHAR columns, FirstName, LastName, and Email, with maximum lengths of 50, 50, and 100 characters, respectively. It is important to note that the storage size of an NVARCHAR column is twice the maximum length, as each character occupies two bytes of storage.

Difference between VARCHAR and NVARCHAR

In SQL Server, VARCHAR and NVARCHAR data types are used for storing character data. The main difference between the two is the maximum length and character size.

VARCHAR data type stores non-Unicode character data, whereas NVARCHAR data type stores Unicode character data. The maximum length of a VARCHAR data type is 8,000 characters, whereas the maximum length of an NVARCHAR data type is 4,000 characters.

As each character in an NVARCHAR column occupies two bytes of storage, the maximum storage size of an NVARCHAR column is half that of a VARCHAR column with an equal maximum length.

Creating a New Table with NVARCHAR Column

To create a new table with NVARCHAR columns in SQL Server, we can use the CREATE TABLE statement with NVARCHAR keyword and the maximum length of the string. An example of creating a new table with NVARCHAR columns is shown below:

CREATE TABLE Customer

(

ID INT PRIMARY KEY IDENTITY,

FirstName NVARCHAR(50),

LastName NVARCHAR(50),

Address NVARCHAR(200),

PhoneNumber NVARCHAR(20)

)

In this example, the Customer table has four NVARCHAR columns, FirstName, LastName, Address, and PhoneNumber, with maximum lengths of 50, 50, 200, and 20 characters, respectively.

Changing String Length of a Column using ALTER TABLE ALTER COLUMN Statement

To change the string length of an NVARCHAR column in SQL Server, we can use the ALTER TABLE ALTER COLUMN statement. An example of changing the string length of an NVARCHAR column is shown below:

ALTER TABLE Customer

ALTER COLUMN PhoneNumber NVARCHAR(50)

In this example, the PhoneNumber column in the Customer table has been altered to allow a maximum length of 50 characters.

Inserting Data into NVARCHAR Column

To insert data into an NVARCHAR column in SQL Server, we can use the INSERT INTO statement with the NVARCHAR column name and string value. An example of inserting data into an NVARCHAR column is shown below:

INSERT INTO Customer (FirstName, LastName, Address, PhoneNumber)

VALUES (‘John’, ‘Doe’, ‘123 Main Street’, ‘(123) 456-7890’)

In this example, the FirstName, LastName, Address, and PhoneNumber columns in the Customer table are populated with string values.

Error Handling for Inserting Data Greater than the Defined String Length

SQL Server has built-in error handling mechanisms that prevent inserting data into an NVARCHAR column greater than the defined string length. When trying to insert data greater than the defined string length, SQL Server throws an error indicating that the string or binary data would be truncated.

To avoid this error, we should ensure that the data being inserted is within the defined string length.

Finding Number of Characters and Storage Size of Values Stored in NVARCHAR Column using LEN and DATALENGTH Functions

To find the number of characters and storage size of values stored in an NVARCHAR column in SQL Server, we can use the LEN and DATALENGTH functions. The LEN function returns the number of characters in the string value, whereas the DATALENGTH function returns the storage size of the string value in bytes.

An example of using the LEN and DATALENGTH functions is shown below:

SELECT FirstName, LEN(FirstName) AS ‘Number of Characters’, DATALENGTH(FirstName) AS ‘Storage Size’

FROM Customer

In this example, the LEN and DATALENGTH functions are used to find the number of characters and storage size of the FirstName column in the Customer table.

Conclusion

In conclusion, the NVARCHAR data type in SQL Server is used for storing Unicode character strings with variable lengths. This article has covered the different aspects of NVARCHAR, including its syntax, column declaration, and differences between VARCHAR and NVARCHAR data types.

It has also explored different examples of using NVARCHAR, including creating a new table with NVARCHAR columns, inserting data into NVARCHAR columns, error handling for inserting data greater than the defined string length, and finding the number of characters and storage size of values stored in NVARCHAR columns using LEN and DATALENGTH functions. By understanding the concepts covered in this article, users can better utilize NVARCHAR data type in their SQL Server databases.

In summary, the NVARCHAR data type in SQL Server is a crucial tool for storing Unicode character strings with variable lengths. This article has delved into its syntax, column declaration, and the differences between VARCHAR and NVARCHAR data types.

It has also detailed different examples of using NVARCHAR, including creating tables, inserting data, error handling, and using functions such as LEN and DATALENGTH to retrieve data. Understanding this data type is important for those who use SQL Server, as it allows for efficient and effective storage of character data.

Remember to use NVARCHAR when storing Unicode character strings with variable lengths, and always ensure to stay within defined string limits.

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