Question

是否可以在codeigniter中执行类似的操作：

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();
}

我为了演示目的简化了查询...但实际上它非常复杂，这就是为什么我决定使用query()方法。

但是查询中没有包含limit子句......我已经通过启用控制器中的codeigniter探查器进行了验证，我可以看到查询是在没有任何限制子句的情况下运行的。

您能告诉我如何使用query()方法完成此操作吗？

修改1

我修改了我的模型，看起来像这样：

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。根据剖析器，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select语句。

Answer 1

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;
   }
}

如果您包含完整查询，则可以更轻松地解决问题或向您展示更好，更有效的方法。

Answer 2

最后，我手动完成所有事情。

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 3

我试过这种方式，多次加入start和limit。你根据选择删除了连接。

    $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();

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');

SELECT field1 FROM（tablename）

$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');

// SELECT field2 FROM（tablename）

Answer 5

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

如何在CodeIgniter中组合query（）和limit（）方法

5 个答案: