如何比较mysql

Question

我有以下两张表，请参阅图片

表1：predefined_attributes

表2：product_detail

我正在尝试比较varchar字段，这是我尝试过的

        `select product_id,category_id,color_name,style_name,
    case when color_name not in (select attribute_column_value from predefined_attributes where category_id=1 and attribute_column_name='color_name') then 1 else 0 END + 
    case when style_name not in (select attribute_column_value from predefined_attributes where category_id=1 and attribute_column_name='style_name') then 1 else 0 END as total_mismatch_count
    from product_detail where product_id in (123456,234567) and category_id=1;`

这是查询结果，请参阅图片

查询结果

实际上，total_mismatch_count shoud返回0，但它显示2为total_mismatch_count。

我已经使用下面的查询检查了设备color_classs表中的attribute_column_value for color_name和style_name，并且我没有看到输出和product_detail输出之间的任何差异。

`select attribute_column_value from predefined_attributes where category_id=1 and attribute_column_name in ('color_name','style_name') and attribute_column_value in ('Green','Pink','Basic','Classic');`

我做错了什么？，比较varchar的最佳方法是什么，以便mysql查询返回total_mismatch_count为0，这是正确的结果？

注意：我也更新了这两个表，以便它没有任何空格

    `update predefined_attributes set attribute_column_value=
    trim(replace(replace(replace(attribute_column_value,'\t',''),'\n',''),'\r',''));`

请帮忙。

Answer 1

我无法测试它，但是类似的东西：

SELECT Count(*) as total_mismatch_count
FROM 
 predefined_attributes p_a
 LEFT JOIN product_detail p_d1 ON p_d1.attribute_column_name = 'color_name'
    AND p_d1.category_id  = p_a.category_id
    AND p_d1.color_name = p_a.attribute_column_value
 LEFT JOIN product_detail p_d2 ON p_d2.attribute_column_name = 'style_name'
    AND p_d2.category_id  = p_a.category_id
    AND p_d2.style_name= p_a.attribute_column_value
WHERE p_d2.category_id IS NULL or p_d1.category_id IS NULL