在 codeigniter SQL 上设置变量答案

【问题标题】：SET variable on codeigniter SQL在 codeigniter SQL 上设置变量
【发布时间】：2013-02-22 07:30:35
【问题描述】：

我试过这段代码：

SET @num := 0, @type := NULL;
SELECT categories_name, products_name, products_url, categories_id, 
       @num := IF( @type = categories_name, @num +1, 1 ) AS row_number,
       @type := categories_name AS dummy
  FROM (
        SELECT categories_name, products_name, products_url, ptc.categories_id
          FROM toc_products_description pd
         INNER JOIN toc_products_to_categories ptc ON pd.products_id = ptc.products_id
         INNER JOIN toc_categories_description cd ON cd.categories_id = ptc.categories_id
               AND pd.language_id =1
               AND cd.language_id =1
        ) AS x
 GROUP BY x.categories_name, x.products_name, x.products_url, x.categories_id
HAVING row_number <=2

在 SQL 上（并且运行良好），现在我需要使用 query() 在 codeigniter 上实现此代码。问题是我无法插入

SET @num := 0, @type := NULL;

在 query() 上，因为我插入时它总是给出错误消息。

我已经这样做了：

$query="SELECT categories_name, products_name, products_url, categories_id, @num := IF( @type := categories_name, @num +1, TRUE) AS row_number, @type := categories_name AS dummy
                FROM (
                SELECT categories_name, products_name, products_url, ptc.categories_id
                FROM toc_products_description pd
                INNER JOIN toc_products_to_categories ptc ON pd.products_id = ptc.products_id
                INNER JOIN toc_categories_description cd ON cd.categories_id = ptc.categories_id
                AND pd.language_id =1
                AND cd.language_id =1
                ) AS x
                GROUP BY x.categories_name, x.products_name, x.products_url, x.categories_id
                HAVING row_number <=5";        
        $result = $this->db->query($query);

我不能在 SELECT 语法之前写任何东西，因为当我尝试它时它会返回错误消息。

【问题讨论】：

标签： sql codeigniter codeigniter-2

【解决方案1】：

您必须为此运行两个单独的查询

$query  =   "SET @num := 0, @type := NULL";
$this->db->query($query);
$new_query  =   "
                SELECT categories_name, products_name, products_url, categories_id, 
                       @num := IF( @type = categories_name, @num +1, 1 ) AS row_number,
                       @type := categories_name AS dummy
                  FROM (
                        SELECT categories_name, products_name, products_url, ptc.categories_id
                          FROM toc_products_description pd
                         INNER JOIN toc_products_to_categories ptc ON pd.products_id = ptc.products_id
                         INNER JOIN toc_categories_description cd ON cd.categories_id = ptc.categories_id
                               AND pd.language_id =1
                               AND cd.language_id =1
                        ) AS x
                 GROUP BY x.categories_name, x.products_name, x.products_url, x.categories_id
                HAVING row_number <=2";
$this->db->query($new_query);

【讨论】：

非常感谢您，先生！我以前试过这个，忘记添加第一个查询（）。现在它运行良好！谢谢。

【解决方案2】：

使用您的 SQL 创建一个存储过程并从 query() 调用该存储过程

【讨论】：

我不能在 SELECT 之前写任何语法
SET ... 和您的整个 select 语句都将在同一个存储过程中，因此您的 $query 将只是 CALL YourSPName (mysql) 或 EXEC YourSPName (sql server)

【解决方案3】：

写入模型

public function select_datos($param1) {
    if ($param1 == 'planilla') {
        $query1 = "SET @numero := 0, @type := NULL";
        $this->db->query($query1);
        $this->db->select('*');
        $this->db->select("@numero:=@numero+1 AS 'posicion'");
        $this->db->from($param1);
        $query = $this->db->get();
        $row['planilla'] = $query->row();
    } else {
        $query = '1'; //    Error
    }
    return $query->result();
}

【讨论】：

请edit 解释为什么这段代码回答了这个问题。