Disable SHOW CREATE TABLE and SHOW COLUMNS in Yii
为啥会显示：SHOW CREATE TABLE and SHOW COLUMNS
答案：
This is how ActiveRecord retrieves the schema to power it's attributes.
Since AR public properties are fetched from DB each time while using the
model, this can cause additional workload for the web server which is
actually not needed for production mode.
(因为当运用模型（model)时，AR的一些公共属性都会从DB中获取，这样会导致服务器负担一些额外的资源开销，实际上对于成品来说，服务器这些开始销是多余的，故应该阻止这种默认行为，可以利用yii的缓存阻止）
Database schema can be cached like in the following example:
Yii database config:
'db'=>array(
...
'schemaCachingDuration'=>86400, // time in seconds
...
),
Enable Yii cache:
（开启yii缓存）
'cache'=>array(
'class' => 'CFileCache',
),
注意：开发阶段可以把这个打开，成品可以开开缓存
参考：http://www.yiiframework.com/forum/index.php/topic/22559-stopping-show-columnsshow-create-table/