LEFT JOIN（mysql）

左表

SELECT TYPE , days 
FROM leavetypes 


type days 
anual 10 

casual 6 

sick 10

右表

SELECT sub_leave_type, (
SUM(working_days) 
) AS used 
FROM vacations 
WHERE `user_id` = '1' 
AND `from_date` 
BETWEEN '2012-01-01' 
AND '2012-12-31' 
GROUP BY sub_leave_type 


sub_leave_type  used 

anual    3 

casual    6

其实我这样做对CakePHP的，这是我的代码。

$allleaves = $this->Leavetype->find('all', array(
     'joins' => array(
      array(
       'table' => 'vacations', 
       'alias' => 'vacationsJoin', 
       'type' => 'left', 
       'conditions' => array('vacationsJoin.sub_leave_type = Leavetype.type') 
      ) 
     ), 
     'conditions' => array(
      'vacationsJoin.user_id' => $_SESSION['Auth']['User']['id'], 
      'vacationsJoin.from_date BETWEEN ? and ?' => array(date('Y') . '-01-01', 
       date('Y') . '-12-31') 
     ), 
     'fields' => array('type', 'days', '(SUM(working_days)) as used'), 
     'group' => 'sub_leave_type', 
      )); 

    $this->set(compact('allleaves'));

这不是出了什么我想要的，我想要的是左表的所有行和其他人休假表

来源

2012-03-05 Milina Udara

你究竟需要什么？你如何加入这些表格？你尝试了什么，什么不起作用？在MySQL中，LEFT JOIN和其他大多数SQL语言一样，你可以像你习惯的那样编写它，它应该可以工作。 – 2012-03-05 10:03:12

你也可以回答你自己的问题。 – 2012-03-05 14:12:57

我说得对，这里的问题就是答案。主要问题在组

$allleaves = $this->Leavetype->find('all', array(
     'joins' => array(
      array(
       'table' => 'vacations', 
       'alias' => 'vacationsJoin', 
       'type' => 'left', 
       'conditions' => array('vacationsJoin.sub_leave_type = Leavetype.type', 
        'vacationsJoin.user_id' => $_SESSION['Auth']['User']['id'], 
      'vacationsJoin.from_date BETWEEN ? and ?' => array(date('Y') . '-01-01', 
       date('Y') . '-12-31'),'vacationsJoin.status'=>'approved' 
        ) 
      ) 
     ), 

     'fields' => array('type', 'days', '(SUM(working_days)) as used'), 
     'group' => 'type' 
      )); 
    $this->set(compact('allleaves'));

来源

2012-03-06 08:27:41

根据您的要求，请阅读此查询，并改变它

SELECT column_name(s) 
FROM table_name1 
LEFT JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

来源

2012-03-05 09:57:16

LEFT JOIN（mysql）

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