SQL--面试题

表A字段如下 
month  name income 
月份   人员 收入

1      a    1000

2      a    2000

3      a    3000
要求用一个SQL语句（注意是一个）得到所有人（不区分人员）每个月及上月和下月的总收入 
要求列表输出为 
月份 当月收入 上月收入 下月收入 
  2    2000    1000    3000

SELECT
	o. MONTH,
	sum(o.income) AS cur,
	(
		SELECT
			sum(t.income)
		FROM
			t5 t
		WHERE
			t. MONTH = (o. MONTH + 1)
		GROUP BY
			t. MONTH
	) AS next,
	(
		SELECT
			sum(t.income)
		FROM
			t5 t
		WHERE
			t. MONTH = (o. MONTH - 1)
		GROUP BY
			t. MONTH
	) AS last
FROM
	t5 o
GROUP BY
	o. MONTH