如何用CakePHP嵌套连接?

原来你不能。至少不能使用上面提供的语法,也不能使用cakephp1.2.6。我检查了来源(耶!到开源框架!)找到了文件 cake/libs/model/datasources/dbo_source.php 它包含连接的代码。

DboSource::renderStatement() 哪条路走的很浅 $query['joins'] 数组,通过 DboSource::buildJoinStatement($join) ,它对参数进行整理(填空等),然后调用 DboSource::renderJoinStatement 创建单个join子句的SQL片段。

我:

我被告知不要在报纸上编辑东西 cake/libs dbo_source.php app/models/datasources/ 用于编辑。然后,我拿起斧子,重构了这条浅浅的小路 $query['joins'] 数组输入 DboSource::renderStatement() DboSource::buildJoinStatementArray() 产生这两种方法:

function buildStatement($query, $model) {
    $query = array_merge(array('offset' => null, 'joins' => array()), $query);

    # refactored (extract method) to make recursion easier
    $query['joins'] = $this->buildJoinStatementArray($query['joins']);

    return $this->renderStatement('select', array(
        'conditions' => $this->conditions($query['conditions'], true, true, $model),
        'fields' => implode(', ', $query['fields']),
        'table' => $query['table'],
        'alias' => $this->alias . $this->name($query['alias']),
        'order' => $this->order($query['order']),
        'limit' => $this->limit($query['limit'], $query['offset']),
        'joins' => implode(' ', $query['joins']),
        'group' => $this->group($query['group'])
    ));
}
/**
 * Replaces the join statement array syntax with SQL join clauses.
 */
function buildJoinStatementArray($joins) {
    if (!empty($joins)) {
        $count = count($joins);
        for ($i = 0; $i < $count; $i++) {
            if (is_array($joins[$i])) {
                $joins[$i] = $this->buildJoinStatement($joins[$i]); # $joins[$i] now contains something like "LEFT JOIN users As User on User.group_id = Group.id"
            }
        }
    }
    return $joins;
}

曾经我有 DboSource::buildJoinStatementArray() ,是时候改变了 DboSource::buildJoinStatement() -我只是加了张支票 $data['joins'] 另一种渲染方法是:

function buildJoinStatement($join) {
    $data = array_merge(array(
        'type' => null,
        'alias' => null,
        'table' => 'join_table',
        'conditions' => array()
    ), $join);

    if (!empty($data['alias'])) {
        $data['alias'] = $this->alias . $this->name($data['alias']);
    }
    if (!empty($data['conditions'])) {
        $data['conditions'] = trim($this->conditions($data['conditions'], true, false));
    }

    # allow for nested joins
    if (!empty($data['joins']) and is_array($data['joins'])) {
        $data['joins'] = $this->buildJoinStatementArray($data['joins']);
        return $this->renderNestedJoinStatement($data);
    }
    else
    {
        return $this->renderJoinStatement($data);
    }
}

新的 renderNestedJoinStatement() 方法与 DboSource::renderJoinStatement() :

/**
 * Renders a final SQL JOIN that contains nested join statements
 *
 * @param array $data
 * @return string
 */
function renderNestedJoinStatement($data) {
    extract($data);
    $nestedJoins = implode(' ', $joins);
    return trim("{$type} JOIN ({$table} {$alias} {$nestedJoins})ON ({$conditions})");
}

TableA hasMany TableB.
TableA hasMany TableC.

TableB belongsTo TableA.

TableC belongsTo TableA.
TableC belongsTo TableD. (might be hasOne)

TableD hasMany TableC. (might be hasOne)

$this->TableA->find(
  'all',
  array(
    'contain' => array(
      'TableB',
      'TableC' => array(
        'TableD'
      )
    ),
    'conditions' => array(...),
    'order' => array(...)
  )
);

如果需要选取特定字段,则需要在contain参数中指定它们,例如,这里我限制TableB的返回字段:

$this->TableA->find(
  'all',
  array(
    'contain' => array(
      'TableB' => array(
        'fields' => array(
          'field_1',
          'field_2'
        ),
      ),
      'TableC' => array(
        'TableD'
      )
    ),
    'conditions' => array(...),
    'order' => array(...)
  )
);

返回的数据应该是这样的:

  [0] => array(
    [TableA] => array(
      [id] => 12,
      [name] => 'Foo'
    ),
    [TableB] => array(
      [id] => 23,
      [table_a_id] => 12,
      [name] => 'Bah'
    ),
    [TableC] => array(
      [id] => 45,
      [table_a_id] => 12,
      [table_d_id] => 67,
      [name] => 'Woo',
      [TableD] => array(
        [0] => array(
          [id] => 67,
          [table_a_id] => 12,
          [name] => 'Wah'
        )
      )
    )
  )

但是,我从来没有在嵌套表是容器(TableD和TableC)的父级的情况下这样做过,所以它可能不起作用,但可能值得一试。