如何在 CodeIgniter 中结合 query() 和 limit() 方法

Question

是否可以在codeigniter中做这样的事情：

publi function getcat($category_id)
{
    $query = "(SELECT cat.id, cat.title ";
    $query = $query . "FROM bf_categories cat ";
    $query = $query . "WHERE cat.id=" . $category_id;
    $this->db->limit(2, 4);
    $records = $this->db->query($query);
    return $records->result();
}

我为了演示的目的简化了查询……但它实际上相当复杂，这就是我决定使用query() 方法的原因。

但查询中未包含限制子句...我已通过在控制器中启用 codeigniter 分析器进行验证，我可以看到查询在没有任何限制子句的情况下运行。

您能告诉我如何使用query() 方法完成此操作吗？

编辑 1

我已将模型修改为如下所示：

public function get_categories_and_products($limit=5, $offset=0, $category_id=null)
{
    print "<BR>the function got the following offeset: $offset and limit: $limit";
    $query = "(SELECT cat.category_id, cat.title, cat.image_thumb, cat.deleted, cat.display_weight ";
            $query = $query."FROM bf_categories cat ";
            $query = $query."WHERE cat.parent_id=".$category_id;
    $query = $query." AND cat.category_id <>".$category_id;
    $query = $query.") UNION (";
    $query = $query."SELECT p.product_id, p.name, p.image_thumb, p.deleted , p.display_weight";
    $query = $query." FROM bf_product p ";
    $query = $query."Inner join bf_product_category cp ";
    $query = $query."on p.product_id=cp.product_id ";
    $query = $query."Where cp.category_id=".$category_id.") ?";

            $records = $this->db->query($query,array($this->db->limit(2, 4)));
            return $records->result();
     }

我现在已经硬编码了限制值......但最终，我将使用传递给方法的值。不幸的是，这段代码仍然不起作用。 根据分析器，这是正在执行的内容：

(SELECT cat.category_id, cat.title, cat.image_thumb, cat.deleted, cat.display_weight FROM bf_categories cat WHERE cat.parent_id=3 AND cat.category_id <>3) UNION (SELECT p.product_id, p.name, p.image_thumb, p.deleted , p.display_weight FROM bf_product p Inner join bf_product_category cp on p.product_id=cp.product_id Where cp.category_id=3)

SELECT * FROM (`bf_categories`) WHERE `category_id` = '3' LIMIT 4, 2

所以它创建了两个单独的选择语句。

Answer 1

你可以使用

$query = "(SELECT cat.id, cat.title ";
$query = $query."FROM bf_categories cat ";
$query = $query."WHERE cat.id=".$category_id." ?";

$this->db->query($query,array($this->db->limit(2, 4)));

或

 $this->db->select('id,title')->from('bf_categories ')->where('id', $id)->limit(2, 4);

link to doc

Answer 2

这是 CI 中查询的样子：

$this->db->select("id, title");
$this->db->where("id", $category_id);
$this->db->from("bf_categories");
$this->db->limit($limit);
$query = $this->db->get();

if($query->num_rows() > 0)
{
   foreach($query->result() as $row)
   {
      echo $row->title;
   }
}

如果您包含完整的查询，解决问题或向您展示更好、更有效的方法会更容易。

Answer 3

最后，我都是手动完成的。

public function get_categories_and_products($limit=10, $offset=0, $category_id=null)
{
    $query = "(SELECT cat.category_id, cat.title, cat.image_thumb, cat.deleted, cat.display_weight ";
    $query = $query."FROM bf_categories cat ";
    $query = $query."WHERE cat.parent_id=".$category_id;
    $query = $query." AND cat.category_id <>".$category_id;
    $query = $query.") UNION (";
    $query = $query."SELECT p.product_id, p.name, p.image_thumb, p.deleted , p.display_weight";
    $query = $query." FROM bf_product p ";
    $query = $query."Inner join bf_product_category cp ";
    $query = $query."on p.product_id=cp.product_id ";
    $query = $query."Where cp.category_id=".$category_id.") limit ".$offset.','.$limit;
    $catsandprods= $this->db->query($query);
    return $catsandprods->result();
}

Answer 4

http://code-igniter.ru/user_guide/database/active_record.html

$this->db->start_cache();
$this->db->select('field1');
$this->db->stop_cache();
$this->db->get('tablename');

从 (tablename) 中选择 field1

$this->db->select('field2');
$this->db->limit(10);
$this->db->get('tablename');

// SELECT field1, field2 FROM (tablename) 限制 10

$this->db->flush_cache();
$this->db->select('field2');
$this->db->get('tablename');

// 选择field2 FROM (tablename)

Answer 5

我尝试过这种方式，使用 start 和 limit 进行多重连接。您根据选择删除加入。

    $this->db->select('*');
    $this->db->from('tbl_requestservice as r');
    $this->db->join('tbl_service as s','s.service_id=r.service_id');
    $this->db->limit($limit, $start);
    $query = $this->db->get();
    print_r($query->result());
    return $query->result();