Can yii execute sql?

1. Create CDbCommand command object

$sql = "select * from users where id=1";
$connection=Yii::app()->db;
$command=$connection->createCommand($sql);

2. Execution of SQL statement

The CDbCommand object has two (kinds) methods to execute SQL statements.

2.1 execute() method

is used for data update (non-query) operations (INSERT, UPDATE and DELETE), and returns the number of record rows affected by the operation. .

$rowCount=$command->execute();

2.2 query() and queryXXX() methods

are used for queries, corresponding to the SELECT statement.

2.2.1 query() method

$dataReader=$command->query();
返回CDbDataReader对象，注意这代表结果集而不是记录，可以通过以下方法来获取（遍历）记录：
// CDbDataReader::read()可以一次获取一行数据，到末尾时返回false
while(($row=$dataReader->read())!==false) 
// CDbDataReader实现了迭代器接口因此可以使用foreach遍历
foreach($dataReader as $row)
// 一次性返回所有的记录(数组)
$rows=$dataReader->readAll();

2.2.2 Derived queryXXX() method

#返回所有结果记录数组
$rows=$command->queryAll();
#返回第一行记录
$row=$command->queryRow();      // query and return the first row of result
#返回所有记录的第一列
$column=$command->queryColumn(); // query and return the first column of result
#返回第一行记录的第一列
$value=$command->queryScalar();  // query and return the first field in the first row

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