将PHP PDO查询写为`dbName`.`tableName`而不是`tableName`-为什么? [英] Write PHP PDO queries as `dbName`.`tableName` as opposed to `tableName` - why?

问题描述

我正在用PHP PDO编写用户注册函数，并且发现我的查询只有在这样写的情况下才能正常运行:

I'm writing a user registration function in PHP PDO, and I have found that my query will only run fine if it is written like this:

<?php
    $dbHost="localhost";
    $dbName="project";
    $dbUser="admin";
    $dbPassword="abcd";
    $dbh=new PDO("mysql:host=$dbHost;dbName=$dbName", $dbUser, $dbPassword);
    $dbh->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
    $query=$dbh->prepare("INSERT INTO project.users (userName, userEmail) VALUES (?,?)");
.....

另一方面，如果我这样写，它将无法运行:

On the other hand, it will not run if I write:

...
$query=$dbh->prepare("INSERT INTO users (userName, userEmail) VALUES (?,?)");
...

在这种情况下，我收到以下错误消息:

In that case, I get the following error message:

致命错误:消息为'SQLSTATE [3D000]的未捕获异常'PDOException':无效的目录名称:1046未选择数据库'在C:\ wamp \ www \ Tests \ Test03 \ Index.php:11堆栈跟踪:#0 C:\ wamp \ www \ Tests \ Test03 \ Index.php(11):PDOStatement-> execute()#1 {main}抛出于第11行的C:\ wamp \ www \ Tests \ Test03 \ Index.php

为什么我需要精确project.users?既然数据库名称本身已经在PDO对象中，为什么输入表名称还不够?

Why is it that I need to precise project.users? Why isn't it enough to enter the table name, given that the db name itself is already in the PDO object?

谢谢！

JDelage

更新，请参阅下面的接受的答案.用dbname=$dbName替换dbName=$dbName可解决此问题.

UPDATE Please see accepted answer below. Replacing dbName=$dbName with dbname=$dbName solves this problem.

推荐答案

显然，PDO无法将活动数据库设置为项目"，因此您需要每次都指定它.

Apparently PDO was unable to set active database to be "project" and therefore you need to specify it every time.

尝试修改您的行，使其看起来像这样:

Try to modify your line to look like this:

$dbh=new PDO("mysql:host=$dbHost;dbname=$dbName", $dbUser, $dbPassword);

唯一的区别是dbname拼写为小写而不是您的dbName.

The only difference is that dbname is spelled all lower-case instead of yours dbName.

或者，在成功建立连接后执行以下SQL命令: USE project;，例如

Alternatively, execute this SQL command after successfully establishing a connection: USE project;, e.g.

$dbh->exec('USE project;');

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