mysql 获取当前某条数据，并把当前数据的前后两条查询出来

MySql 通过id获取当前某条数据，并把当前数据的前后两条查询出来

思路：

1. 给查询数据每项记录增加一个行号用行号记录查询顺序
2. 通过id获取目标记录，返回该记录行号，并把行号存到变量（如@nn）
3. 通过变量@nn-1 定位到前一条，通过@nn+1定位后一条
4. 然后通过 in 过滤 （@nn, @nn-1, @nn+1）三条记录即可

select * from (select @num:=@num+1 row_num, n.* from news n, (select @num:=0) s order by n.time desc ) a

where a.row_num in (

select @nn:=b.row_num as row_num from (select @num2:=@num2+1 row_num, n.* from news n, (select @num2:=0) s order by n.time desc) b

where b.id=199

union all

select @nn-1 as row_num

union all

select @nn+1 as row_num

);