TEXT and NTEXT Data Types

The TEXT and NTEXT data types in SQL Server are used to store large character strings. While they were widely used in older versions, Microsoft recommends using VARCHAR(MAX) and NVARCHAR(MAX) respectively for new development due to their enhanced functionality and performance.

TEXT Data Type

The TEXT data type stores non-Unicode character data. It can store up to 2^31 - 1 (2,147,483,647) bytes of data. Each character in TEXT typically occupies 1 byte, depending on the code page of the database.

Characteristics of TEXT:

Stores character data.
Maximum size: 2 GB.
Character encoding is dependent on the database's collation.
Cannot be directly used in many string functions or compared with character data stored in VARCHAR columns without explicit conversion.

When to Use TEXT (Legacy):

Note: The TEXT data type is considered a legacy type. It is recommended to migrate existing TEXT columns to VARCHAR(MAX).

Maintaining compatibility with older applications or databases.
When dealing with large amounts of non-Unicode text data that cannot be easily converted.

NTEXT Data Type

The NTEXT data type stores Unicode character data. It can store up to 2^31 - 1 (2,147,483,647) characters. Each character in NTEXT typically occupies 2 bytes.

Characteristics of NTEXT:

Stores Unicode character data (supports international characters).
Maximum size: 2 GB.
Each character uses 2 bytes of storage.
Cannot be directly used in many string functions or compared with character data stored in NVARCHAR columns without explicit conversion.

When to Use NTEXT (Legacy):

Note: The NTEXT data type is considered a legacy type. It is recommended to migrate existing NTEXT columns to NVARCHAR(MAX).

Storing text data that requires support for a wide range of characters, such as multiple languages.
Maintaining compatibility with older applications or databases.

Migration Recommendation: VARCHAR(MAX) and NVARCHAR(MAX)

Recommendation: For all new development, and for migrating existing TEXT and NTEXT data, Microsoft strongly recommends using VARCHAR(MAX) and NVARCHAR(MAX) respectively.

Benefits of VARCHAR(MAX) and NVARCHAR(MAX):

Unified Functions: They work seamlessly with standard string functions, unlike TEXT and NTEXT.
Improved Performance: Often offer better performance and more efficient storage mechanisms.
Greater Flexibility: Can store up to 2 GB of data, similar to TEXT/NTEXT, but with more modern features.
Standardization: Aligns with the SQL standard for large object data.

Example: Migrating TEXT to VARCHAR(MAX)


                    -- Add a new column with VARCHAR(MAX) type

                    ALTER TABLE YourTable

                    ADD NewTextColumn VARCHAR(MAX);

                    

                    -- Copy data from the old TEXT column to the new VARCHAR(MAX) column

                    UPDATE YourTable

                    SET NewTextColumn = CAST(OldTextColumn AS VARCHAR(MAX));

                    

                    -- Optionally, drop the old TEXT column after verification

                    -- ALTER TABLE YourTable DROP COLUMN OldTextColumn;

                    

                    -- Rename the new column to match the old one if desired

                    -- EXEC sp_rename 'YourTable.NewTextColumn', 'OldTextColumn', 'COLUMN';

Limitations and Considerations

When working with TEXT and NTEXT, be aware of the following:

Function Compatibility: Many string manipulation functions (e.g., SUBSTRING, LEFT, RIGHT) and comparison operators have specific behavior or limitations when used with TEXT and NTEXT. You often need to use CAST or CONVERT to compatible types (like VARCHAR or NVARCHAR) to use these functions reliably.
Performance: Operations on TEXT and NTEXT columns can sometimes be slower than on their MAX counterparts, especially for large datasets or complex queries.
Indexing: Indexing on TEXT and NTEXT columns is not directly supported. You would typically need to index computed columns based on a prefix of the TEXT/NTEXT data or use Full-Text Search.

Full-Text Search Integration

For advanced searching capabilities within TEXT and NTEXT (or VARCHAR(MAX)/NVARCHAR(MAX)) columns, SQL Server provides Full-Text Search. This feature allows for linguistic searching, phrase searching, and proximity searching, which are more powerful than simple pattern matching.

Example: Creating a Full-Text Index


                    -- Ensure Full-Text Search is installed and enabled for the database

                    -- Enable Full-Text Search on the table

                    ENABLE FULLTEXT ON YourTable; 

                    

                    -- Create a Full-Text Catalog if one doesn't exist

                    CREATE FULLTEXT CATALOG MyCatalog AS DEFAULT;

                    

                    -- Create a Full-Text Index on the TEXT/NTEXT column

                    CREATE FULLTEXT INDEX ON YourTable(OldTextColumn TYPE COLUMN) 

                    KEY INDEX PK_YourTable_ID 

                    ON MyCatalog 

                    WITH CHANGE_TRACKING AUTO; 

                    

                    -- Example Query using CONTAINS for Full-Text Search

                    SELECT * FROM YourTable 

                    WHERE CONTAINS(OldTextColumn, '"SQL Server" NEAR "documentation"');

Summary

While TEXT and NTEXT were functional for storing large text data, their limitations in function compatibility and indexing make them less desirable for modern database development. Migrating to VARCHAR(MAX) and NVARCHAR(MAX) is the recommended approach for improved performance, flexibility, and ease of use.

Tip: Always test performance and compatibility thoroughly after migrating data types. Consider using Full-Text Search for robust text searching requirements.

SQL Server Documentation

TEXT and NTEXT Data Types

TEXT Data Type

Characteristics of TEXT:

When to Use TEXT (Legacy):

NTEXT Data Type

Characteristics of NTEXT:

When to Use NTEXT (Legacy):

Migration Recommendation: VARCHAR(MAX) and NVARCHAR(MAX)

Benefits of VARCHAR(MAX) and NVARCHAR(MAX):

Example: Migrating TEXT to VARCHAR(MAX)

Limitations and Considerations

Full-Text Search Integration

Example: Creating a Full-Text Index

Summary