gstlouis's questions

我正在尝试从数据库级别计算一些东西，并想知道是否可以使用 if/else 或 ifnull 或其他来评估它？如果不是什么是好方法？

有可能以这种方式做某事吗？

我尝试了几种方法，但这是我的最新示例。

IF (SELECT markups.markup FROM markups LIMIT 1) 
THEN
    SELECT ((SELECT AVG(products.price) FROM products WHERE products.code = "8G435G232AB") * (SELECT markups.markup FROM markups LIMIT 1)) + (SELECT AVG(products.price) FROM products WHERE products.code = "8G435G232AB") AS code_8G435G232AB FROM products ORDER BY products.code LIMIT 1
ELSE
    SELECT AVG(products.price) FROM products WHERE products.code = "8G435G232AB"

我有两个表，attributes 和 attributes_entries

attributes 保存标题，attribute_entries 保存该标题的值。

如果我做：

SELECT attribute_entries.title AS ent_title, 
       attributes.title AS attr_title 
FROM   attribute_entries 
INNER JOIN attributes 
       ON attribute_entries.FK_attribute_id = attributes.id 
WHERE attribute_entries.title = 'ford' 
      AND attributes.title = 'manufacturer'

我可以得到以下结果：

ent_title | attr_title
ford      | manufacturer

如果我做另一个查询：

SELECT attribute_entries.title AS ent_title, 
       attributes.title AS attr_title 
FROM   attribute_entries 
INNER JOIN attributes 
      ON attribute_entries.FK_attribute_id = attributes.id 
WHERE attribute_entries.title = 'whatev' 
      AND attributes.title = 'nickname'

我得到以下结果：

ent_title | attr_title
whatev    | nickname
whatev    | nickname

这两个查询都与我在那里的数据一致。

所以我认为这会起作用：

SELECT attribute_entries.title AS ent_title, 
       attributes.title AS attr_title 
FROM attribute_entries 
INNER JOIN attributes 
      ON attribute_entries.FK_attribute_id = attributes.id 
WHERE attribute_entries.title = 'ford' 
      AND attributes.title = 'manufacturer' 
      AND attribute_entries.title = 'whatev' 
      AND attributes.title = 'nickname'

这显然是行不通的。在一份声明中获得结果的最佳方法是什么？