问题描述
我有一个名为bank的表，该表具有三列: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，该查询将根据缺口返回余额，并且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
有人在这里看到我在做什么错吗?
Can anyone see what I am doing wrong here?
推荐答案
反引号(`)用于标识，例如表名，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.
您想这样做:
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
如果不存在歧义，并且表/列名称没有特殊字符或空格，则可以将`保留为空.
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.
这是一些干燥且难以阅读的文档: http: //dev.mysql.com/doc/refman/5.0/zh-CN/identifiers.html
Here is some documentation that is dry and hard to read: http://dev.mysql.com/doc/refman/5.0/en/identifiers.html
但这是有关dba.stackoverflow的一个相关问题，该问题更易于阅读:
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，我建议大家阅读: http://www.sitepoint.com/forums/showthread.php?408497-the-big-bad-thread-of -"MySQL最佳实践和其他有用信息"
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！