我正在用 MySQL 客户端的时候，突然想到如果可以给查询结果添加排名该多好啊，然后就找到了一个简单的解决办法。
下面是一个示例表的数据：
然后我们要根据 Roll_No 字段进行排序并给出排名，我们首先必须定义一个初始值为0的变量，然后在查询结果中使用这个变量。
如下面的代码：
SET @counter=0; SELECT @counter:=@counter+1 AS Rank,LastName,Roll_no as Roll FROM Students ORDER BY Roll_
执行该语句的结果如下：
更多关于自定义变量的内容请看 MySQL 的文档。
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