Cakephp中自定义查询的分页问题，解决方法

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Cakephp的默认分页功能是基于内置的表关联模型的，所以，如果我们有更多复杂的要求，比如：

    联合两张表的查询分页

这样Cakephp的默认分页就达不到我们的要求，解决的方法是：

使用自定义的查询分页

使用自定义查询分页需要在模型中重载两个方法，paginate()和paginateCount()

1. paginate()

提供分页的数据支持，原型如下：
1. function paginate( $conditions , $fields , $order , $limit , $page = 1, $recursive = null);

参数由Cakephp自定传递，使用方法和find方法是一样的，参数通过在Controller中定义paginate变量传递，例如：
1. $limit = 5;
2. $this ->paginate = array (
3.      'SavedNote' => compact( 'limit' )
4. );

注意：

如果重载paginate()的函数使用参数，请自己格式化参数为自己定义的格式，Cakephp不会自动格式化参数。

2. paginateCount()

提供分页的数据数量统计支持，原型如下：
1. function paginateCount( $conditions = null, $recursive = 0);

带来的问题

通过上述的方法确实能够给我们的自定义查询分页，但是问题是，这样做之后我们无法再使用原有的模型的分页。

解决方法：

使用额外的模型完成我们的自定义查询任务

我们新建一个模型，/models/saved_note.php ，代码如下：
view source
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print ?
01. <?php
02. class SavedNote extends AppModel {
03.      var $name = 'SavedNote' ;
04. 
05.      //这个模型不使用任何表，它仅仅为我们提供自定义分页支持
06.      var $useTable = false;
07.      var $user_id = 0;
08. 
09.      /*
10.       * Paginate Function
11.      */
12.      function paginate( $conditions , $fields , $order , $limit , $page = 1, $recursive = null) {
13.          $offset = ((int) $page - 1) * (int) $limit ;
14.          $conditions = "
15.          //这里省略的SQL会在附录中列出
16.          ";
17.          return $this ->query( $conditions );
18.      }
19. 
20.      /*
21.       * Paginate Count Function
22.      */
23.      function paginateCount( $conditions = null, $recursive = 0) {
24.          $conditions = "
25.          //这里省略的SQL会在附录中列出
26.          ";
27.          $result = $this ->query( $conditions );
28.          return (int) $result [0][0][ 'NUMS' ];
29.      }
30. }
31. ?>

我们可以在控制器中使用这个自定义查询了：
view source
< id="highlighter_859578_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" id="highlighter_859578_clipboard" type="application/x-shockwave-flash" title="copy to clipboard" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_859578" menu="false" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" width="16" height="16">
print ?
01. class NotesController extends AppController{
02.      var $name = 'Notes' ;
03.      var $layout = 'notes' ;
04. 
05.      //这里引入我们需要的模型
06.      var $uses = array ( 'Note' , 'SavedNote' , 'TrashNote' );
07. 
08.      function saved(){
09.          $user_id = $this ->Auth->User( 'id' );
10.          $limit = 5;
11. 
12.          //这里为我们的自定义查询，传递一些参数
13.          $this ->paginate = array (
14.              'SavedNote' => compact( 'limit' )
15.          );
16.          $this ->SavedNote->user_id = $user_id ;
17. 
18.          //控制器的paginate方法，会自定寻找模型的相应方法，并调用
19.          $notes = $this ->paginate( 'SavedNote' );
20.          $this ->set(compact( 'notes' ));
21.      }
22. 
23. }

最后，希望大家看到的是，自定义模型中的paginate参数的使用是需要自己手动解析和分配的，如果要使用Cakephp的默认查询样式，还需要自己解析一下。

附录：

1. 模型中paginate方法用到的SQL
view source
< id="highlighter_998076_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" id="highlighter_998076_clipboard" type="application/x-shockwave-flash" title="copy to clipboard" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_998076" menu="false" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" width="16" height="16">
print ?
01. SELECT
02.      DISTINCT (SavedNote.note_id),
03.      SavedNote.*,
04.      Note.subject,
05.      Note.body,
06.      Note.created,
07.      SentUser. name ,
08.      ReceivedUser. name
09. FROM (
10.      SELECT
11.          ReceivedNote.note_id AS note_id,
12.          ReceivedNote.receive_user_id AS receive_user_id,
13.          ReceivedNote.send_user_id AS send_user_id,
14.          ReceivedNote.is_deleted AS is_deleted,
15.          ReceivedNote.is_saved AS is_saved,
16.          ReceivedNote.read_date AS read_date,
17.          'received' as src
18.      FROM
19.          received_notes AS ReceivedNote
20.      WHERE
21.          receive_user_id = {$this->user_id}
22.      UNION ALL
23.      SELECT
24.          SentNote.note_id AS note_id,
25.          SentNote.receive_user_id AS receive_user_id,
26.          SentNote.send_user_id AS send_user_id,
27.          SentNote.is_deleted AS is_deleted,
28.          SentNote.is_saved AS is_deleted,
29.          SentNote.read_date AS read_date,
30.          'sent' as src
31.      FROM
32.          sent_notes AS SentNote
33.      WHERE
34.          send_user_id = {$this->user_id}
35. ) as SavedNote
36. LEFT JOIN notes AS Note ON Note.id = SavedNote.note_id
37. LEFT JOIN users AS SentUser ON SentUser.id = SavedNote.send_user_id
38. LEFT JOIN users AS ReceivedUser ON ReceivedUser.id = SavedNote.receive_user_id
39. WHERE
40. SavedNote.is_saved = 1
41. ORDER BY
42. Note.created DESC
43. LIMIT {$offset},{$limit}

2. 模型中paginateCount方法用到的SQL
view source
< id="highlighter_96965_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" id="highlighter_96965_clipboard" type="application/x-shockwave-flash" title="copy to clipboard" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_96965" menu="false" src="http://www.thinkly.cn/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" width="16" height="16">
print ?
01. SELECT
02.      COUNT ( DISTINCT (SavedNote.note_id)) AS NUMS
03. FROM (
04.      SELECT
05.          ReceivedNote.note_id AS note_id,
06.          ReceivedNote.receive_user_id AS receive_user_id,
07.          ReceivedNote.send_user_id AS send_user_id,
08.          ReceivedNote.is_saved AS is_saved,
09.          'received' as src
10.      FROM
11.          received_notes AS ReceivedNote
12.      WHERE
13.          receive_user_id = {$this->user_id}
14.      UNION ALL
15.      SELECT
16.          SentNote.note_id AS note_id,
17.          SentNote.receive_user_id AS receive_user_id,
18.          SentNote.send_user_id AS send_user_id,
19.          SentNote.is_saved AS is_saved,
20.          'received' as src
21.      FROM
22.          sent_notes AS SentNote
23.      WHERE
24.          send_user_id = {$this->user_id}
25. ) as SavedNote
26. WHERE
27. SavedNote.is_saved = 1