How to Dynamically Pivot Data in MySQL Using Prepared Statements?

Dynamic Pivoting in MySQL Using Prepared Statements

MySQL lacks a native PIVOT function, but you can emulate it using aggregate functions and CASE statements. For dynamically pivoting data, prepared statements offer an efficient solution.

Consider a scenario with a table of product parts:

CREATE TABLE Parts (
    part_id INT,
    part_type VARCHAR(1),
    product_id INT
);
INSERT INTO Parts (part_id, part_type, product_id) VALUES
(1, 'A', 1),
(2, 'B', 1),
(3, 'A', 2),
(4, 'B', 2),
(5, 'A', 3),
(6, 'B', 3);

The desired output is a pivoted table summarizing the part IDs for each product:

product_id  part_A_id  part_B_id
----------  ----------  ----------
1           1          2
2           3          4
3           5          6

Dynamic Pivoted Query

SET @sql = NULL;
SELECT GROUP_CONCAT(DISTINCT
    CONCAT(
        'max(case when part_type = ''',
        part_type,
        ''' then part_id end) AS part_',
        part_type, '_id'
    )
) INTO @sql
FROM Parts;
SET @sql = CONCAT('SELECT product_id, ', @sql, '
                  FROM Parts
                   GROUP BY product_id');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

Static Pivoted Query (Limited Columns)

For a static query with a fixed number of pivot columns:

SELECT product_id,
    max(CASE WHEN part_type = 'A' THEN part_id END) AS part_A_id,
    max(CASE WHEN part_type = 'B' THEN part_id END) AS part_B_id
FROM Parts
GROUP BY product_id;

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