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在查询数据库的时候,我们有时候需要对查询出来的数据加上序列,1,2,3,……n
例如:我们根据表的某个字段排序后,要对这些数据加上序列,这个时候序号常常不是我们建表时设置好的自增的主键id,怎么办呢????
可能我们会用变量来解决,如下
set @rownum=0;
SELECT @rownum:=@rownum+1 AS rownum, table_name.*
FROM table_name
如果在数据库中要用一句SQL语句来实现,这又改怎么办呢????
oracle数据库有专门的rownum来解决伪序列问题,但是mysql却到目前为止还没有内置的函数等来解决此问题
这个问题也困扰了我一段时间,到各种论坛上发帖也没有能回答,最后在无意间找到了这种解决方法
SELECT @rownum:=@rownum+1 AS rownum, table_name.*
FROM (SELECT @rownum:=0) r, table_name
把rownum的设置初值放到了from 和需要查询的表的前面
原文来自“老鸟的大心脏”,在这里谢谢他。
希望能帮助更多需要帮助的人……
也希望更多的高手们提出更多的漂亮的方法……
也许有人也会用到存储过程来解决,那也是一个方法,我曾经也用过,但是后来不能用存储过程了,就悲剧了
摘自 ystyaoshengting的专栏
bitsCN.com
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