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Home Backend Development PHP Tutorial SQL中“ ` ”的作用是什么?

SQL中“ ` ”的作用是什么?

Jun 06, 2016 pm 08:09 PM
php sql

看到别人的代码,

<code>'SELECT '.$param['field'].' FROM `'.DBPRE.$param['table']</code>
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from后面的`这个符号有什么作用呢?

回复内容:

看到别人的代码,

<code>'SELECT '.$param['field'].' FROM `'.DBPRE.$param['table']</code>
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from后面的`这个符号有什么作用呢?

所有的数据库都有类似的设置,不过mysql用的是`而已。通常用来说明其中的内容是数据库名、表名、字段名。例如

<code>select from from table;</code>
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第一个from是字段名,最后的table也是字段名,但是同时也是mysql关键字,这样执行的时候就会报错,所以应该使用

<code>select `from` from `table`</code>
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当然,为了便于阅读,不建议使用关键字作为字段名、表名,同时,应该对数据库名、表名、字段名用一对儿反引号包含。

避免和关键字冲突,就是告诉mysql里面的是普通字符串,不是啥命令

避免和 mysql 的本身的关键字 冲突 所以 用这个符号括起来 虽然有时候不影响 查询 但是最好是要 加上的

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