O Guia Definitivo do Yii 1.1

$user = Yii::app()->db->createCommand()
->select('id, username, profile')
->from('tbl_user u')
->join('tbl_profile p', 'u.id=p.user_id')
->where('id=:id', array(':id'=>$id))
->queryRow();
The Query Builder is best used when you need to assemble a SQL statement procedurally,
or based on some conditional logic in your application. The main benefits of using the
Query Builder include:
• It allows building complex SQL statements programmatically.
• It automatically quotes table names and column names to prevent conflict with SQL
reserved words and special characters.
• It also quotes parameter values and uses parameter binding when possible, which
helps reduce risk of SQL injection attacks.
• It offers certain degree of DB abstraction, which simplifies migration to different DB
platforms.
• It is not mandatory to use the Query Builder. In fact, if your queries are simple, it is
easier and faster to directly write SQL statements.
Preparing Query Builder
The Yii Query Builder is provided in terms of CDbCommand, the main DB query class
described in Data Access Objects.
To start using the Query Builder, we create a new instance of CDbCommand as follows,
$command = Yii::app()->db->createCommand();
That is, we use Yii::app()->db to get the DB connection, and then call
CDbConnection::createCommand() to create the needed command instance.
Note that instead of passing a whole SQL statement to the createCommand() call as we
do in Data Access Objects, we leave it empty. This is because we will build individual parts
of the SQL statement using the Query Builder methods explained in the following.
Building Data Retrieval Queries
Data retrieval queries refer to SELECT SQL statements. The query builder provides a set
of methods to build individual parts of a SELECT statement. Because all these methods
return the CDbCommand instance, we can call them using method chaining, as shown in
the example at the beginning of this section.
• select: specifies the SELECT part of the query
• selectDistinct: specifies the SELECT part of the query and turns on the DISTINCT
flag
• from: specifies the FROM part of the query