Why Use the 'N' Prefix in T-SQL String Literals?

Detailed explanation of the 'N' prefix in T-SQL string literals

In T-SQL queries, you may encounter situations where you use the prefix 'N' before inserting a string value into a table. This non-intuitive representation has a specific purpose and it is important to understand its significance.

The role of 'N' prefix

The 'N' prefix indicates that the string to be inserted is in Unicode format, specifically an nchar, nvarchar, or ntext data type. These data types store character data using a consistent character encoding, regardless of the database's default character set.

When to use 'N'

Using the 'N' prefix is ​​critical when you insert strings that contain non-ASCII characters, such as foreign letters or special symbols. This ensures that the string is stored correctly and can be retrieved without data corruption.

For example, in the query provided:

<code class="language-sql">INSERT INTO Personnel.Employees
VALUES(N'29730', N'Philippe', N'Horsford', 20.05, 1);</code>

'Philippe' For French accented characters in the name, the 'N' prefix ensures that the data is stored in Unicode format, allowing correct representation of these characters.

The Importance of Unicode Data

Using Unicode data is critical as it allows cross-platform compatibility and ensures consistent representation of characters across different systems and languages. By prepending 'N' to a string, you can prevent data loss or corruption due to differences in character encodings.

Alternatives to 'N' prefix

In some cases, you can use the COLLATE clause to specify a specific character set for a string literal. This is useful if you want to convert a string to a specific encoding before inserting.

Example:

<code class="language-sql">INSERT INTO Personnel.Employees
VALUES('29730', COLLATE Latin1_General_CI_AS 'Philippe', COLLATE Latin1_General_CI_AS 'Horsford', 20.05, 1);</code>

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