MySQL将行透视成动态列数

不幸的是，MySQL没有

PIVOT

CASE

select pt.partner_name,  count(case when pd.product_name = 'Product A' THEN 1 END) ProductA,  count(case when pd.product_name = 'Product B' THEN 1 END) ProductB,  count(case when pd.product_name = 'Product C' THEN 1 END) ProductC,  count(case when pd.product_name = 'Product D' THEN 1 END) ProductD,  count(case when pd.product_name = 'Product E' THEN 1 END) ProductEfrom partners ptleft join sales s  on pt.part_id = s.partner_idleft join products pd  on s.product_id = pd.prod_idgroup by pt.partner_name

请参阅SQL演示

由于您不了解产品，因此您可能希望动态执行此操作。这可以使用准备好的语句来完成。

使用动态数据透视表（将行转换为列），您的代码将如下所示：

SET @sql = NULL;SELECt  GROUP_CONCAt(DISTINCT    CONCAt(      'count(case when Product_Name = ''',      Product_Name,      ''' then 1 end) AS ',      replace(Product_Name, ' ', '')    )  ) INTO @sqlfrom products;SET @sql = CONCAt('SELECt pt.partner_name, ', @sql, ' from partners ptleft join sales s  on pt.part_id = s.partner_idleft join products pd  on s.product_id = pd.prod_idgroup by pt.partner_name');PREPARE stmt FROM @sql;EXECUTE stmt;DEALLOCATE PREPARE stmt;

请参阅SQL演示

可能值得注意的

GROUP_CONCAT

SET@@group_concat_max_len = 32000;