在mysql里面，我们偶尔会有这样的sql出现：
select userid,count(userid) as cnt from xxxxxtable group by userid;
这样的sql在mongo里怎么实现呢？其实也相对比较简单
PHP代码
- <?php
- $mongo = new Mongo();
- $mongo->selectDB('xxx');//库
- $collection = $mongo->selectCollection('表');
- $field = array('userid'=>1);
- $cnt = array('cnt'=>0);
- $result = $collection->group($field,$cnt,"function(obj,pref){pref.cnt++;}");
打印出来的结果也很方便识别：
XML/HTML代码
- Array
- (
- [retval] => Array
- (
- [0] => Array
- (
- [userid] => 11111
- [cnt] => 2
- )
- //省略
- )
- [count] => 21
- [keys] => 11
- [ok] => 1
- )
果然轻轻松松啊
