SQL中“ ` ”的作用是什么?
看到别人的代码,
<code>'SELECT '.$param['field'].' FROM `'.DBPRE.$param['table']</code>
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>
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>
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>
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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