求这个sql语句如何写

求这个sql语句怎么写！
表a:
        字段：         month           salary

要求：查询每个月的该月月份、工资、上一个月工资、下一个月工资
显示格式：month       salary         lastsalary       nextsalary

[解决办法]
lead,lag()函数实现
[解决办法]

SQL code

select month,salary,lag(salary,1,null) lastsalary,lead(salary,1,null)nextsalary from a
[解决办法]
如果表中月份是按顺序排列的话  上面可以了 不是的话 可以先排序再获取  或者使用add_mongths()来计算获取
[解决办法]
探讨

SQL code

select month,salary,
lag(salary,1,null) lastsalary,
lead(salary,1,null)nextsalary 
from a

[解决办法]
SQL code
SELECT MONTH,SALARY,LEAD(SALARY,1,SALARY)OVER(ORDER BY MONTH) LASTSALARY,       LAG(SALARY,1,SALARY)OVER(ORDER BY MONTH) NEXTSALARY  FROM( SELECT MONTH,SUM(SALARY) SALARY FROM T GROUP BY MONTH ) T1;
[解决办法]

with  a
as
(
select 2006 salary,6 month from dual
union select 2007 salary,7 month from dual
union select 2008 salary,8 month from dual
)
select month,salary,
lag(salary,1,null) over(order by month) lastsalary,
lead(salary,1,null) over(order by month) nextsalary 
from a