SQL Server 2016

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

DROP TABLE IF EXISTS #CommentsTable;

-- Step 1: Create a sample table and insert test data
CREATE TABLE #CommentsTable (
    ID INT PRIMARY KEY,
    Comments VARCHAR(MAX)
);

-- Insert a sample comment with 280,000 characters
INSERT INTO #CommentsTable (ID, Comments)
VALUES (1, REPLICATE('A', 280000));  -- Example comment

-- Step 2: Declare chunk size
DECLARE @ChunkSize INT = 64750;

-- Step 3: Generate a Numbers Table Using CROSS JOIN (Tally Table) for each comment
WITH L1(N) AS 
(
    -- Create a Tally table with 100 NULLs
    SELECT 1 FROM (VALUES
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),
        (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)
    ) t(N)
),
iTally(N, StartPos) AS 
(
    -- Generate a Tally Table using CROSS JOIN
    SELECT 
        ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1 AS N,
        (ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1) * @ChunkSize + 1 AS StartPos
    FROM L1 a CROSS JOIN L1 b CROSS JOIN L1 c  -- Creating up to 1 million rows
),
SplitComments AS 
(
    -- Calculate comment chunks
    SELECT 
        t.ID,
        it.N + 1 AS PartId,
        SUBSTRING(t.Comments, it.StartPos, @ChunkSize) AS CommentPart
    FROM #CommentsTable t
    JOIN iTally it 
        ON it.StartPos <= LEN(t.Comments) -- Ensure we don’t go beyond the comment length
        AND it.StartPos + @ChunkSize - 1 > it.StartPos
) 
-- Final selection
SELECT 
    ID, 
    PartId, 
    CommentPart
FROM SplitComments
ORDER BY ID, PartId;

ID	PartId	CommentPart
1	1	                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    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