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

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

<?php
            #数据库连接
            $dbtype = 'mysql';
            $host = 'localhost';
            $db = 'test';
            $user = 'root';
            $psw = '19sucai';
            
            $dsn = $dbtype . ':host=' . $host . ';' . 'dbname=' . $db;
            
            try {
                $dbh = new PDO($dsn, $user, $psw, array(PDO::ATTR_PERSISTENT=>true));
                echo '连接成功<br>';
            } catch(Exception $e) {
                die('Connect Failed Message: ' . $e->getMessage());
            }
            
            #使用query函数查询
            $sql = 'SELECT * FROM user';
            $query = $dbh->query($sql);
            $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
            $rs = $query->fetchAll();
            var_dump($rs);
            
            #使用exec函数进行INSERT,UPDATE,DELETE,结果返回受影响的行数
            $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
            // $rs = $dbh->exec($sql);
            // var_dump($rs) . '<br>';
            
            #使用prepareStatement进行CURD
            $sql = 'SELECT * FROM user WHERE userId = ?';
            $stmt = $dbh->prepare($sql);
            $stmt->bindParam(1, $userId);    //绑定第一个参数值
            $userId = 1;
            
            $stmt->execute();
            $stmt->setFetchMode(PDO::FETCH_ASSOC);
            $rs = $stmt->fetchAll();
            var_dump($rs);
            
            #使用事务
            try {
                $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);    //设置错误模式,发生错误时抛出异常
                $dbh->beginTransaction();
                $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
                $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
                $stmt1 = $dbh->prepare($sql1);
                $stmt2 = $dbh->prepare($sql2);
                $stmt1->bindParam(1, $userId);
                $stmt2->bindParam(1, $userId);
                $userId = 1;
                $stmt1->execute();
                $stmt2->execute();
                $dbh->commit();
            } catch(Exception $e) {
                $dbh->rollBack();
                die('Transaction Error Message: ' . $e->getMessage());
            }
?>