使用codeigniter进行MySQL查询（活动记录）

Question

我在 codeigniter 中使用以下查询：

$this->db->select('products.id,
                   categories.name as cat_name, 
                   products.name as name,
                   products.product_image,
                   products.description,
                   products.price,
                   products.furl,
                   products.on_sale,
                   products.quantity_in_stock,
                   products.product_code,
                   products.rating_1,
                   products.rating_2,
                   products.rating_3,
                   products.rating_4,
                   products.rating_5,
                   products.rated_by,
                   products.discount,
                   ((products.rating_1+products.rating_2,
                     products.rating_3,
                     products.rating_4,
                     products.rating_5)/rated_by  as calc)
');

检查 calc 附近的 sql 语法时出现错误。请解释问题出在哪里以及原因。 p.s：我只是想在 order by 子句中使用 calc，如下所示：

$this->db->order_by('calc','desc');
$this->db->get();

更新：这是我在执行此查询时得到的结果：

Error Number: 1064

您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，了解在第 1 行的 'as calc) FROM (

products

) JOIN

categories

ON

categories

.

id

=

products

.`ca' 附近使用的正确语法

Answer 1

如果您要使用别名，那么您将不希望 CodeIgnioter 自动在您的列名称周围添加勾号，因为它会破坏一切。只需将

select()

的第二个参数设置为

false

即可关闭此行为：

$this->db->SELECT(  
                 'products.id,categories.name as cat_name,  
                  products.name as name,  
                  products.product_image,  
                  products.description,  
                  products.price,  
                  products.furl,  
                  products.on_sale,  
                  products.quantity_in_stock,  
                  products.product_code,  
                  products.rating_1,  
                  products.rating_2,  
                  products.rating_3,  
                  products.rating_4,  
                  products.rating_5,  
                  products.rated_by,  
                  products.discount,  
                  ((products.rating_1+products.rating_2,  
                    products.rating_3,products.rating_4,  
                    products.rating_5)/rated_by  as calc)', false)  ;

Answer 2

是的，你是对的@John

$this->db->select('
    products.id,
    categories.name as cat_name,
    products.name as name,
    products.product_image,
    products.description,
    products.price,
    products.furl,
    products.on_sale,
    products.quantity_in_stock,
    products.product_code,
    products.rating_1,
    products.rating_2,
    products.rating_3,
    products.rating_4,
    products.rating_5,
    products.rated_by,
    products.discount,
    (
        (products.rating_1 + products.rating_2,
         products.rating_3,
         products.rating_4,
         products.rating_5
        )
        / rated_by  as calc
    )
', false) ;

也为我工作