mysql - 在单个查询中以不同条件两次从同一列获取值

Question

Hii 我想在单个查询中以不同的条件两次从同一列获取值

这是我的代码

SELECT
    o.products_options_name,
    ov.products_options_values_name AS products_options_values_name,
    a.options_values_quantity  
FROM
    table_products_options o,
    table_products_attributes a
WHERE
    a.options_id = o.products_options_id
    AND 
    o.products_options_values_id = a.options_values_id 
    AND
    a.products_id = :products_id 
    AND
    a.options2_values_id = options2_values_id

我想在不同的条件下再次获取列 products_options_values_name 的值，例如在同一查询中的 where a.options2_values_id = ov.products_options_values_id。我该怎么做？

Answer 1

尝试使用 UNION 运算符，

SELECT o.products_options_name, ov.products_options_values_name AS products_options_values_name,
a.options_values_quantity  
FROM 
table_products_options o, table_products_attributes a
WHERE 
a.options_id = o.products_options_id AND ov.products_options_values_id = a.options_values_id 
AND a.products_id = :products_id1 AND 
a.options2_values_id = options2_values_id 

UNION 

SELECT o.products_options_name, ov.products_options_values_name AS products_options_values_name,
 a.options_values_quantity  
FROM 
table_products_options o, table_products_attributes a
WHERE 
a.options_id = o.products_options_id AND ov.products_options_values_id = a.options_values_id
AND a.products_id = :products_id2 AND 
a.options2_values_id = options2_values_id