AI_GENERATE_CHUNKS (Transact-SQL)

Applies to: SQL Server 2025 (17.x) Preview

AI_GENERATE_CHUNKS is a table-valued function that creates "chunks", or fragments of text based on a type, size, and source expression.

Compatibility level 170

AI_GENERATE_CHUNKS requires the compatibility level to be at least 170. When the level is less than 170, the Database Engine is unable to find the AI_GENERATE_CHUNKS function.

To change the compatibility level of a database, refer to View or change the compatibility level of a database.

Syntax

Transact-SQL syntax conventions

AI_GENERATE_CHUNKS (source = text_expression
                    , chunk_type = 'FIXED'
                   [ [ , ] chunk_size = numeric_expression ]
                   [ [ , ] overlap = numeric_expression ]
)

Arguments

source

An expression of any character type (for example, nvarchar, varchar, nchar, or char).

chunk_type

A string literal naming the type or method to chunk the text/document and can't be NULL or a value from a column.

Accepted values for this release:

• FIXED

chunk_size

When chunk_type is FIXED, this parameter sets the character/word count size of each chunk specified as a variable, a literal, or a scalar expression of type tinyint, smallint, int, or bigint. chunk_size can't be NULL, negative, or zero (0).

overlap

The overlap parameter determines the percentage of the preceding text that should be included in the current chunk. This percentage is applied to the chunk_size parameter to calculate the size in characters. The overlap value can be specified as a variable, a literal, or a scalar expression of type tinyint, smallint, int, or bigint. It must be a whole number between zero (0) and 50, inclusive, and cannot be NULL or negative. The default value is zero (0).

Return types

AI_GENERATE_CHUNKS returns a table with the following columns:

Return example

Here's an example of the return results of AI_GENERATE_CHUNKS with the following parameters:

• Chunk type of FIXED.

• Chunk size of 50 characters.

• Chunk text: All day long we seemed to dawdle through a country which was full of beauty of every kind. Sometimes we saw little towns or castles on the top of steep hills such as we see in old missals; sometimes we ran by rivers and streams which seemed from the wide stony margin on each side of them to be subject to great floods.

Remarks

AI_GENERATE_CHUNKS can be used on a table with multiple rows. Depending on the chunk size and the amount of text being chunked, the result set indicates when it starts a new column or document with the chunk_set_id column. In the following example, the chunk_set_id changes when it finishes chunking the text of the first row and moves to the second. The values for chunk_order and chunk_offset also reset to indicate a new starting point.

CREATE TABLE textchunk (text_id INT IDENTITY(1,1) PRIMARY KEY, text_to_chunk nvarchar(max));
GO

INSERT INTO textchunk (text_to_chunk)
VALUES
('All day long we seemed to dawdle through a country which was full of beauty of every kind. Sometimes we saw little towns or castles on the top of steep hills such as we see in old missals; sometimes we ran by rivers and streams which seemed from the wide stony margin on each side of them to be subject to great floods.'),
('My Friend, Welcome to the Carpathians. I am anxiously expecting you. Sleep well to-night. At three to-morrow the diligence will start for Bukovina; a place on it is kept for you. At the Borgo Pass my carriage will await you and will bring you to me. I trust that your journey from London has been a happy one, and that you will enjoy your stay in my beautiful land. Your friend, DRACULA')
GO

SELECT c.*
FROM textchunk t
CROSS APPLY
   AI_GENERATE_CHUNKS(source = text_to_chunk, chunk_type = N'FIXED', chunk_size = 50) c

Examples

A. Chunk a text column with FIXED type and size of 100 characters

The following example uses AI_GENERATE_CHUNKS to chunk a text column. It uses a chunk_type of FIXED and a chunk_size of 100 characters.

SELECT
    c.chunk
FROM
   docs_table t
CROSS APPLY
   AI_GENERATE_CHUNKS(source = text_column, chunk_type = N'FIXED', chunk_size = 100) c

B. Chunk a text column with overlap

The following example uses AI_GENERATE_CHUNKS to chunk a text column using overlap. It uses the chunk_type of FIXED, a chunk_size of 100 characters, and an overlap of 10 percent.

SELECT
    c.chunk
FROM
   docs_table t
CROSS APPLY
   AI_GENERATE_CHUNKS(source = text_column, chunk_type = N'FIXED', chunk_size = 100, overlap = 10) c

C. Use AI_GENERATE_EMBEDDINGS with AI_GENERATE_CHUNKS

This example uses AI_GENERATE_EMBEDDINGS with AI_GENERATE_CHUNKS to create embeddings from text chunks and then inserts the returned vector arrays from the AI model inferencing endpoint into a table.

INSERT INTO
    my_embeddings (chunked_text, vector_embeddings)
SELECT
    c.chunk,
    AI_GENERATE_EMBEDDINGS(c.chunk USE MODEL MyAzureOpenAiModel)
FROM
    table_with_text t
CROSS APPLY
    AI_GENERATE_CHUNKS(source = t.text_to_chunk, chunk_type = N'FIXED', chunk_size = 100) c

Related content

• AI_GENERATE_EMBEDDINGS (Transact-SQL)
• CREATE EXTERNAL MODEL (Transact-SQL)
• ALTER EXTERNAL MODEL (Transact-SQL)
• DROP EXTERNAL MODEL (Transact-SQL)