如何将普通的SQL查询转换为Zend_Db_Select？

Question

您好，我想将普通的mysql查询转换为zend.db.select；

我想使用以下脚本：

$select = $db->select();

// Add a FROM clause
$select->from( ...specify table and columns... )

// Add a WHERE clause
$select->where( ...specify search criteria... )

// Add an ORDER BY clause
$select->order( ...specify sorting criteria... );

$select->limit(20, 10);

对于我下面的查询

SELECT 
    IF(derived_messages.toid = '$user', derived_messages.fromid, 
    derived_messages.toid) friend1,c.UserName,
    derived_messages.message, derived_messages.fromid, derived_messages.toid,
    derived_messages.is_read,derived_messages.type,derived_messages.id as mesid,                    
    derived_messages.date,
    (SELECT M.message_id FROM messagesmapped M where M.message_id= derived_messages.id AND M.user_id ='$user' AND M.important = 1) as MesMapid
    FROM 
    (               
    SELECT * 
    FROM messages
    WHERE messages.deleted_by NOT 
    IN ( $user ) 
    ORDER BY Date DESC      
    ) derived_messages
    INNER JOIN Users c ON c.MemberID = IF(derived_messages.toid = '$user', derived_messages.fromid, 
    derived_messages.toid)
    WHERE (derived_messages.id IN 
    (SELECT M.message_id FROM messagesmapped M where M.message_id= derived_messages.id AND M.user_id ='$user' AND M.important = 1)                  
    AND 
    (derived_messages.toid='$user' OR derived_messages.fromid='$user'))

    GROUP BY friend1 ASC 
    ORDER BY derived_messages.date DESC, derived_messages.id DESC LIMIT $limit $offset

我希望有人能够在这方面给我帮助。

谢谢。

- devrez

Answer 1

有可能但不太可能有人会为你编写查询语句。

我建议处理这样的查询是将每个子查询都作为自己的Zend_Db_Select对象编写，然后使用已经具有对象的子查询构建最终查询。

Zend_Db_Select不直接支持IF函数，所以您需要使用Zend_Db_Expr将该语句添加到您的选择中。

---

以下是一个基本示例。让我们构建以下查询：

SELECT IF(msg.toId = 'drew010', msg.fromId, msg.toId), id, name, age, history.ip
FROM users
JOIN history ON users.id = history.userId
WHERE users.id = (
    SELECT id FROM users WHERE loginCount > 1000
)
GROUP BY id,
ORDER BY age DESC

首先构建子查询，选择loginCount大于1000的用户。

$subquery1 = $db->select()
                ->from('users', array('id'))
                ->where('loginCount > ?', 1000);

接下来，使用IF函数构建外部查询：

$cols  = array(
    new Zend_Db_Expr('IF(' . $db->quoteInto('msg.toId = ?', 'drew010') . '), msg.fromId, msg.toId'),
    'id', 'name', 'age'
);

$query = $db->select()
            ->from('users', $cols)
            ->join('history', 'users.id = history.userId', array('ip'))
            ->where('id = ?', $subquery1)
            ->group('id')
            ->order('age DESC');

echo $query;

输出结果：

SELECT
  IF(msg.toId = 'drew010', msg.fromId, msg.toId),
  `users`.`id`,
  `users`.`name`,
  `users`.`age`,
  `history`.`ip`
FROM `users`
INNER JOIN `history`
  ON users.id = history.userId
WHERE id = (
    (SELECT `users`.`id`
    FROM `users`
    WHERE (loginCount > 1000))
)
GROUP BY `id`
ORDER BY `age` DESC

所以，正确的做法是先将整个查询分解为单独的查询，然后构建外部查询。只需要耐心并慢慢来。此外，请阅读Zend_Db_Select文档，以全面了解可用的内容。

- drew010