PHP PDO的简单使用(query(),exec(),prepare(),Transaction,行锁)

 1        
 2
 3         true));
15                 echo '连接成功
';
16             } catch(Exception $e) {
17                 die('Connect Failed Message: ' . $e->getMessage());
18             }
19             
20             #使用query函数查询
21             $sql = 'SELECT * FROM user';
22             $query = $dbh->query($sql);
23             $query->setFetchMode(PDO::FETCH_ASSOC);    //设置结果集返回格式,此处为关联数组,即不包含index下标
24             $rs = $query->fetchAll();
25             var_dump($rs);
26             
27             #使用exec函数进行INSERT,UPDATE,DELETE,结果返回受影响的行数
28             $sql = 'INSERT INTO user (`userName`, `userPassword`, `userAge`) SELECT (MAX(userId) + 1), \'123456\', 18 FROM user';    //插入一行用户数据,其中userName使用userId最大值+1
29             // $rs = $dbh->exec($sql);
30             // var_dump($rs) . '
';
31             
32             #使用prepareStatement进行CURD
33             $sql = 'SELECT * FROM user WHERE userId = ?';
34             $stmt = $dbh->prepare($sql);
35             $stmt->bindParam(1, $userId);    //绑定第一个参数值
36             $userId = 1;
37             
38             $stmt->execute();
39             $stmt->setFetchMode(PDO::FETCH_ASSOC);
40             $rs = $stmt->fetchAll();
41             var_dump($rs);
42             
43             #使用事务
44             try {
45                 $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);    //设置错误模式,发生错误时抛出异常
46                 $dbh->beginTransaction();
47                 $sql1 = 'SELECT bookNum FROM book WHERE bookId = ? FOR UPDATE';    //此处加上行锁,可以对bookNum做一些判断,bookNum>1,才做下一步更新操作
48                 $sql2 = 'UPDATE book SET bookNum=bookNum-1 WHERE bookId = ?';    //加上行锁后,如果user1在买书,并且user1的买书过程没有结束,user2就不能执行SELECT查询书籍数量的操作,这样就保证了不会出现只有1本书,却两个人同时买的状况
49                 $stmt1 = $dbh->prepare($sql1);
50                 $stmt2 = $dbh->prepare($sql2);
51                 $stmt1->bindParam(1, $userId);
52                 $stmt2->bindParam(1, $userId);
53                 $userId = 1;
54                 $stmt1->execute();
55                 $stmt2->execute();
56                 $dbh->commit();
57             } catch(Exception $e) {
58                 $dbh->rollBack();
59                 die('Transaction Error Message: ' . $e->getMessage());
60             }
61         ?>