为什么将`放在列周围? [英] Why put ` around columns?

问题描述

在某些代码中，我看到人们将`放在他们的列周围.为什么?与不使用它们有什么区别?

In some code i see people put ` around their columns. Why? IS there any difference from not using them?

SELECT `players`.`name`, `houses`.`id` FROM `players`, `houses` 
WHERE `houses`.`owner` = `players`.`id`

推荐答案

使用反引号可以将保留字用作列名或表名，例如

Using the backquotes allows reserved words to be used as column or table names e.g.

SELECT `values` FROM `references` WHERE `precision` > 0

以及带有非字母数字的名称也必须包含在`"之间，例如.

and names with nonalphanumerics must be enclosed between the "`"s too, e.g.

SELECT `user name` FROM `registered users` WHERE `total score` > 0

请参见 http://dev.mysql.com/doc/refman /5.1/en/identifiers.html 了解详情.

我认为，当动态使用这些名称(例如， (人工示例)

I think this is often seen when those names are used dynamically, e.g. (artificial example)

mysql_prepare_statement("SELECT `%q` FROM `%q` WHERE `%q` > 0", col, tbl, col_cond);

采用这种形式，可以相同地处理任何种类的列名和表名，并且可以避免恶意注入尝试，例如col = "1; DROP TABLE users--".

in this form, any kinds of column and table names can be handled identically, and malicious injection attempts such as col = "1; DROP TABLE users--" can be avoided.

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