本文章简单的介绍了MySQL rownumber SQL生成自增长序号详细测试方法
MySQL 几乎模拟了 Oracle,SQL Server等商业的大部分功能,函数。但很可惜,到目前的版本(5.1.33)为止,仍没有实现ROWNUM这个功能。
下面介绍几种具体的实现方法.
建立实验环境如下
代码如下 | 复制代码 |
> create table tbl ( mysql> insert into tbl values mysql> |
1. 直接在程序中实现;
这应该算是效率最高的一种,也极为方便。直接在你的开发程序中(PHP/ASP/C/...)等中,直接初始化一个变量nRowNum=0,然后在while 记录集时,nRowNum++; 然后输出即可。
2. 使用MySQL变量;在某些情况下,无法通过修改程序来实现时,可以考虑这种方法。
缺点,@x 变量是 connection 级的,再次查询的时候需要初始化。一般来说PHP等B/S应用没有这个问题。但C/S如果connection一只保持则要考虑 set @x=0
代码如下 | 复制代码 |
mysql> select @x:=ifnull(@x,0)+1 as rownum,id,col
|
3. 使用联接查询(笛卡尔积)
缺点,显然效率会差一些。
利用表的自联接,代码如下,你可以直接试一下 select a.*,b.* from tbl a,tbl b where a.col>=b.col 以理解这个方法原理。
代码如下 | 复制代码 |
mysql> select a.id,a.col,count(*) as rownum
|
4. 子查询
缺点,和联接查询一样,具体的效率要看索引的配置和MySQL的优化结果。
代码如下 | 复制代码 |
mysql> select a.*, |

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