SQL 对比,移动累计

数据对比 两种常用模型

1.对比下一行,判断增长、减少、维持现状

-- 建表
drop table sales

create table sales(
num int,
soc int
);
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );
insert into sales values(, );

select a.num, a.soc,
       case when a.soc = b.soc then ''  -- 持平
            when a.soc > b.soc then '+'  -- 增长
            when a.soc < b.soc then '-'  -- 减少
       else '-' end as var
  from sales a left join sales b
    on a.num = b.num +
 order by num

2.累计上个结果 (诺依曼型递归集合)

-- 建表
drop table if exists accounts;
create table accounts(
prc_date date,
prc_amt int8
);
insert into accounts values(,);
insert into accounts values(,);
insert into accounts values(,-);
insert into accounts values(,);
insert into accounts values(,-);
insert into accounts values(,);
insert into accounts values(,);

--测试

select prc_date, a1.prc_amt,
(select sum(prc_amt) from accounts a2
where a1.prc_date >= a2.prc_date) as onhand_amt
from accounts a1
order by prc_date;