How to Dynamically Pivot MySQL Rows into Columns?

MySQL dynamic row to column operation

Question:

Retrieve data from multiple tables and format it into a pivot table with dynamic column headers, even if the exact number of columns is not known in advance.

Original query:

SELECT partners.name, products.name, COUNT(*) 
FROM sales
JOIN products ON sales.products_id = products.id
JOIN partners ON sales.partners_id = partners.id
GROUP BY sales.partners_id, sales.products_id
LIMIT 0, 30

Solution using CASE statement:

MySQL does not have a PIVOT function, so you need to use an aggregate function with a CASE statement:

select pt.partner_name,
  count(case when pd.product_name = 'Product A' THEN 1 END) as ProductA,
  count(case when pd.product_name = 'Product B' THEN 1 END) as ProductB,
  count(case when pd.product_name = 'Product C' THEN 1 END) as ProductC,
  count(case when pd.product_name = 'Product D' THEN 1 END) as ProductD,
  count(case when pd.product_name = 'Product E' THEN 1 END) as ProductE
from partners pt
left join sales s
  on pt.part_id = s.partner_id
left join products pd
  on s.product_id = pd.prod_id
group by pt.partner_name

Dynamic pivot table using prepared statements:

To handle dynamic column headers, you can use prepared statements:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'count(case when Product_Name = ''',
      Product_Name,
      ''' then 1 end) AS ',
      replace(Product_Name, ' ', '')
    )
  ) INTO @sql
from products;

SET @sql = CONCAT('SELECT pt.partner_name, ', @sql, ' from partners pt
left join sales s
  on pt.part_id = s.partner_id
left join products pd
  on s.product_id = pd.prod_id
group by pt.partner_name');

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

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