问题描述

我有一个名为 bank 的表，其中包含三列:uid、nick、balance.

I have a table called bank with three columns: uid, nick, balance.

我正在尝试创建一个查询，该查询将根据昵称返回余额，但在使用此查询时出现错误 Unknown column 'Alex' in 'where clause':

I am trying to create a query that will return the balance based on the nick, and I am getting an error Unknown column 'Alex' in 'where clause' when I use this query:

SELECT b.balance FROM bank AS b WHERE b.nick=`Alex` LIMIT 1

谁能看到我在这里做错了什么?

Can anyone see what I am doing wrong here?

推荐答案

反引号 (`) 用于标识符，如表名、列名等.单引号 (') 用于字符串文字.

backticks (`) are used for identifiers, like table names, column names, etc. Single quotes(') are used for string literals.

你想做:

SELECT b.balance FROM bank AS b WHERE b.nick='Alex' LIMIT 1

或者，更明确地说:

SELECT `b`.`balance` FROM `bank` AS b WHERE `b`.`nick`='Alex' LIMIT 1

如果没有歧义，并且表/列名称没有特殊字符或空格，则可以将 ` 关闭.

When there is no chance of ambiguity, and when table/column names do not have special characters or spaces, then you can leave the ` off.

以下是一些枯燥且难以阅读的文档:http://dev.mysql.com/doc/refman/5.0/en/identifiers.html

Here is some documentation that is dry and hard to read: http://dev.mysql.com/doc/refman/5.0/en/identifiers.html

但这里有一个关于 dba.stackoverflow 的相关问题，它更容易阅读:https://dba.stackexchange.com/questions/23129/benefits-of-using-backtick-in-mysql-queries

But here is a related question on dba.stackoverflow that is easier to read: https://dba.stackexchange.com/questions/23129/benefits-of-using-backtick-in-mysql-queries

这是一个非常好的页面，我推荐大家阅读:http://www.sitepoint.com/forums/showthread.php?408497-the-big-bad-thread-of-quot-MySQL-Best-Practices-and-Other-Useful-Information-quot

And here is a very good page that I recommend everyone read: http://www.sitepoint.com/forums/showthread.php?408497-the-big-bad-thread-of-quot-MySQL-Best-Practices-and-Other-Useful-Information-quot

这篇关于MySQL 错误:“where 子句"中的未知列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！