Yii 使用数据库 之 数据访问对象 (DAO)

简介：

Yii DAO 主要包含如下四个类：
CDbConnection: 代表一个数据库连接。
CDbCommand: 代表一条通过数据库执行的 SQL 语句。
CDbDataReader: 代表一个只向前移动的，来自一个查询结果集中的行的流。
CDbTransaction: 代表一个数据库事务。

#: 执行一个无查询语句execute(): INSERT, UPDATE 和 DELETE 。如果成功，它将返回此执行所影响的行数。

#：执行插入（单条）
$sql = "INSERT INTO test(username,sex) VALUES('张三',1)";
$command = Yii::app()->db_product->createCommand($sql);
$data = $command->execute();        #成功返回1

#：执行单条插入（占位符形式）
$sql = "INSERT INTO test(username,sex) VALUES (:username,:sex)";           #注意占位符不需要引号
$data = Yii::app()->db_product->createCommand($sql)->execute([':username'=>'he',':sex'=>2]);

 #：插入多条（原始语句）
 $sql = "INSERT INTO test(username,sex,add_time) VALUES ('李思',2,NOW() ),('王五',1,NOW())";
 $command = Yii::app()->db_product->createCommand($sql);
 $data = $command->execute();         #成功返回1


#插入多条（构造占位符形式）
$sql = "INSERT INTO test(username,sex) VALUES (:username1,:sex1),(:username2,:sex2)";
$data = Yii::app()->db_product->createCommand($sql)
   ->execute([':username1'=>'he1',':sex1'=>1,':username2'=>'he2',':sex2'=>2]);


#插入多条（构造原始语句）
$params = [
    [
        'username' => '新增1',
        'sex' => 1,
        'add_time' => date('Y-m-d H:i:s')
    ],
    [
        'username' => '新增2',
        'sex' => 1,
        'add_time' => date('Y-m-d H:i:s')
    ]
];
$rows = [];
foreach ($params as $k=>$row){
    $rows[] = "('".implode("','",$row)."')";                   #需要完善，当值带有双引号或单引号的问题
}
$cloums = array_keys(reset($params));                          #构造插入表字段
$sql = 'insert into test';
$sql .= ' ('.implode(',',$cloums).') values '.implode(',',$rows);

#insert into test (username,sex,add_time) values ('新增1','1','2018-08-31 13:54:07'),('新增2','1','2018-08-31 13:54:07')
$data = Yii::app()->db_product->createCommand($sql)->execute();

#插入多条（构造占位符形式）
$placeHolders = [];
$placeParams = [];
$i=1;
foreach ($params as $rows){
    $placeHolder = [];
    foreach ($rows as $kK=>$value){
        $placeHolder[] = ':'.$kK.$i;
        $placeParams[':'.$kK.$i] = $value;                          #构造占位符对应的值
    }
    $placeHolders[] = "(".implode(',',$placeHolder).")";            #构造占位符及sql语句
   $i++;
   unset($placeHolder);
}

$cloums = array_keys(reset($params));
$sql = 'insert into test';
$sql .= ' ('.implode(',',$cloums).') values '.implode(',',$placeHolders);

$data = Yii::app()->db_product->createCommand($sql)->execute($placeParams);


 #：修改
$sql = "update test set username='修改2',sex=2,update_time=now() WHERE id = 2";
$command = Yii::app()->db_product->createCommand($sql);
$data = $command->execute();          #成功返回1

#批量更新：原理语句
//        UPDATE test 
//        SET username = CASE id
//            WHEN 1 THEN 3
//            WHEN 2 THEN 4
//            WHEN 3 THEN 5
//        END,
//        title = CASE id
//            WHEN 1 THEN 'New Title 1'
//            WHEN 2 THEN 'New Title 2'
//            WHEN 3 THEN 'New Title 3'
//        END
//        WHERE id IN (1,2,3)


#代码实现：
#批量修改（单个字段）
$params = [
    '1'=>'赵一"',
    '2'=>'钱二',
    '3'=>'张"三',
    '4'=>"李'四",
    '5'=>'王五',
    '6'=>'刘六'
];

$ids = implode(',', array_keys($params));
$sql = "UPDATE test SET username = CASE id ";
foreach ($params as $id => $ordinal) {
    $sql .= sprintf("WHEN %d THEN '%s' ", $id, addslashes($ordinal));
}
$sql .= "END WHERE id IN ($ids)";
$data = Yii::app()->db_product->createCommand($sql)->execute();



#：删除
$sql = "delete from test where id = 1";
$command = Yii::app()->db_product->createCommand($sql);
$data = $command->execute();          #成功返回1

2、查询

#1.query
$sql = 'select * from test';
$command = Yii::app()->db_product->createCommand($sql);
$dataReader = $command->query();

#1.1 重复调用 read() 直到它返回 false
while(($row=$dataReader->read())!==false) {
  $data[] = $row;
}

#1.2 使用 foreach 遍历数据中的每一行
foreach($dataReader as $row) {
    $data[] = $row;
}

#1.3 一次性提取所有行到一个数组
$data = $dataReader->readAll();

3、queryXXX

#2.查询并返回结果中的所有行:queryAll()
$sql = 'select * from test';
$data = Yii::app()->db_product->createCommand($sql)->queryAll();


#3.查询并返回结果中的第一行
$sql = 'select * from test';
$data = Yii::app()->db_product->createCommand($sql)->queryRow();

#4.查询并返回结果中的第一列
$sql = 'select * from test';
$data = Yii::app()->db_product->createCommand($sql)->queryColumn();

#5.查询并返回结果中第一行的第一个字段
$sql = 'select * from test';
$data = Yii::app()->db_product->createCommand($sql)->queryScalar();

4、绑定参数

#6.绑定参数
$username = '刘老三';
$sex = 1;
$sql="INSERT INTO test (username,sex) VALUES (:username,:sex)";
$command = Yii::app()->db_product->createCommand($sql);
$command->bindParam(':username',$username,PDO::PARAM_STR);      #绑定参数
$command->bindParam(":sex",$sex,PDO::PARAM_INT);
$data  = $command->execute();                           #成功返回1

$id = 1;
$sql = "select * from test where id=:id";
$data = Yii::app()->db_product->createCommand($sql)->bindParam(":id",$id,\PDO::PARAM_INT)->queryAll();

#6.2：批量绑定 ??

5、绑定值

#绑定值
$sql="INSERT INTO test (username,sex) VALUES (:username,:sex)";
$command = Yii::app()->db_product->createCommand($sql);
$command->bindValue(':username','hao',PDO::PARAM_STR);
$command->bindValue(":sex",2,PDO::PARAM_INT);
$data  = $command->execute();


$sql = "select * from test where id=:id";
$data = Yii::app()->db_product->createCommand($sql)->bindValue(":id",2,\PDO::PARAM_INT)->queryAll();