Yii-数据库操作（查）
注：当项目没查找到整个对象会为空需要这样判定if($rows !== null) 当对象不为空
{
return true;
}else{
return false;
}
SELECT，读表时候用到
find（）
第一种find()
// find the first row satisfying the specified condition
$post=Post::model()->find($condition,$params);
// find the row with postID=10
$post=Post::model()->find('postID=:postID', array(':postID'=>10));
同样的语句，用另种方式表示
$criteria=new CDbCriteria;
$criteria->select='title'; // only select the 'title' column
$criteria->condition='postID=:postID';
$criteria->params=array(':postID'=>10);
$post=Post::model()->find($criteria); // $params is not needed
第二种find()
$post=Post::model()->find(array(
'select'=>'title',
'condition'=>'postID=:postID',
'params'=>array(':postID'=>10),
));
// find the row with the specified primary key
$post=Post::model()->findByPk($postID,$condition,$params);
findByAttributes()
$post=Post::model()->findByAttributes($attributes,$condition,$params);
第一种findByAttributes()
$checkuser = user_field_data::model()->findByAttributes(
array('user_id' => Yii::app()->user->user_id, 'field_id' => $fieldid));
第二种findByAttributes()
$checkuser = user_field_data::model()->findByAttributes(
$attributes = array('user_id' => Yii::app()->user->user_id, 'field_id' => $fieldid));
第三种当没有conditions时候，不用params
$user_field_data = user_field_data::model()->findAllByAttributes(
$attributes = array('user_id' => ':user_id'),
$condition = "field_id in (:fields)",
$params = array(':user_id' => Yii::app()->user->user_id, ':fields' => "$rule->dep_fields"));
// find the first row using the specified SQL statement
$post=Post::model()->findBySql($sql,$params);
例子
user_field_data::model()->findBySql("select id from user_field_data where user_id = :user_id and field_id = :field_id ", array(':user_id' => $userid,':field_id'=>$fieldid));
此时回传的是一个对象
第四种 添加其他条件
http://www.yiiframework.com/doc/api/CDbCriteria#limit-detail
$criteria = new CDbCriteria;
$criteria->select ='newtime';//选择只显示哪几个字段要与库中名字相同，但是不能COUNT(newtime) as name这样写
$criteria->join = 'LEFT JOIN Post ON Post.id=Date.id';//1.先要在relation函数中增加与Post表的关系语句 2.Date::model()->with('post')->findAll($criteria)
$criteria->group = 'newtime';
$criteria->limit = 2; // 都是从0开始，选取几个
$criteria-> offset = 2;// 从哪个偏移量开始
print_r(Date::model()->findAll($criteria));
//得到行数目或者其他数目 count
// get the number of rows satisfying the specified condition
$n=Post::model()->count($condition,$params);
// get the number of rows using the specified SQL statement
$n=Post::model()->countBySql($sql,$params);
// check if there is at least a row satisfying the specified condition
$exists=Post::model()->exists($condition,$params);
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