MySQL反引号的作用:    ` `

1.mysql中保留关键字不能用于表名和字段:

比如:create table key (报错)

        create table `key` (正确)

        insert into test(abc) values(‘123’) (报错)

        insert into test(`abc`) values(‘123’) (成功)

MySQL中加入PHP变量:

1.MySQL中加入PHP变量,第一种是用括号来区分变量

举个栗子: $sql = "select * from table where name=‘{$name}’ and age={$age}";

2.或者用”.$v.”来连接:

举个栗子:”insert into shop_good (good,words,author,state,name) values (‘“.$name.”’,5,10,15,20)”;

需要注意的是,这就涉及到PHP的基础知识,”双引号解析变量,单引号不解析变量”.

3.常用格式如1,2但是如果sql语句用"",为了书写简单,PHP变量可以不加单双引号.

举个栗子:$sql = "select * from table where name=$name and age=$age";

或者$sql = "select * from table where name='$name' and age='$age'";