如何在条件聚合mysql中添加where?[副本]

SELECT a.number, a.description, b.attribute_code, b.attribute_value 
FROM items a 
JOIN attr_maps b ON b.number = a.number WHERE a.number = AB123

如果执行查询,结果如下:

我想得出这样的结果:

SELECT i.number, i.description,
       MAX(CASE WHEN am.attribute_code = 'brand' then am.attribute_value END) as brand,
       MAX(CASE WHEN am.attribute_code = 'model' then am.attribute_value END) as model,
       MAX(CASE WHEN am.attribute_code = 'category' then am.attribute_value END) as category,
       MAX(CASE WHEN am.attribute_code = 'subcategory' then am.attribute_value END) as subcategory
FROM items i JOIN
     attr_maps am
     ON am.number = i.number
WHERE i.number = AB123
GROUP BY i.number, i.description

它起作用了

但我还是很困惑的补充 where 条件。所以我想它可以过滤品牌等

我试着这样:

SELECT i.number, i.description,
       MAX(CASE WHEN am.attribute_code = 'brand' then am.attribute_value END) as brand,
       MAX(CASE WHEN am.attribute_code = 'model' then am.attribute_value END) as model,
       MAX(CASE WHEN am.attribute_code = 'category' then am.attribute_value END) as category,
       MAX(CASE WHEN am.attribute_code = 'subcategory' then am.attribute_value END) as subcategory
FROM items i JOIN
     attr_maps am
     ON am.number = i.number
WHERE brand = 'honda'
GROUP BY i.number, i.description

存在错误 Unknown column 'brand' in 'where clause'