## max
~~~php
$max = TestUserListModel::create()->max('age');
~~~
## min
~~~php
$min = TestUserListModel::create()->min('age');
~~~
## count
~~~php
// count 不必传字段名
$count = TestUserListModel::create()->count();
~~~
## avg
~~~php
$avg = TestUserListModel::create()->avg('age');
~~~
## sum
~~~php
$sum = TestUserListModel::create()->sum('age');
~~~
