用两段SQL

union all拼接

在进行字段的减

------------------参考

select sum(a1) as a1,sum(a2) as a2,sum(b1) as b1,sum(b2) as b2

from (

select A  as a1,B as b1,null as a2,null as b2

from tb

where 序号=1

union all

select null as a1,null as b1,A  as a2,B as b2

from tb

where 序号=2)

序号也是数据里的吗？那有两个2和两个1，怎么确定哪个2减哪个1呢，还是直接1和2分别求和算？

利用LAG函数返回结果集中先前行的数据，不过你这个数据要先进性分组才行

select 

    a字段

    , LAG(a字段) OVER (PARTITION BY 分组字段 ORDER BY 序号 ) as 上一行a字段的值

    ,a字段 - LAG(a字段) OVER (PARTITION BY 分组字段 ORDER BY 序号 ) as 差值

from table