php 基于PDO下的exec()函数查询

exec()方法返回执行后受影响的行数。

语法：int PDO::exec(string statement)

提示：

参数statement是要执行的SQL语句。该方法返回执行查询时受影响的行数，通常用于insert,delete和update语句中。但不能用于select查询,返回查询结果。

为了验证这个提示，下面我分别对insert,delete,update,select 查询进行测试；

INSERT

try{
$conn=new PDO("mysql:host=$servername;dbname=$dbname", $username,$password);
$conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$sql="INSERT INTO `hello`(`firstname`,`lastname`,`email`)values('ye','xianming','1150416034@qq.com'),
('xiao','hua','xiaohua@163.com')";
$conn->exec($sql);
echo "Insert record success";
}catch(PDOException $e){
echo "Error:".$e->getMessage();
}

Delete

try{
$conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
$conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$sql="delete from hello where id=61";
$conn->exec($sql);
echo "delete record success";
}catch(PDOException $e){
echo "Error".$e->getMessage();
}

Update

try{
$conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
$conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$sql="UPDATE hello SET firstname='xiao',lastname='ming' WHERE id='62'";
$conn->exec($sql);
echo "update record success";
}catch(PDOException $e){
echo "Error".$e->getMessage();
}

Select

try{
$conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
$conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$sql="select * from hello";
$query=$conn->exec($sql);
for($i=0;$i<count($query);$i++){
print_r($query);
}
echo "select record success";
}catch(PDOException $e){
echo "Error".$e->getMessage();
}

注：上面四种查询方式，最后只有select查询不能正常执行；