sql - 在 Sybase 中获取与上个月关联的字段
问题描述
在下面的查询中,我试图BALANCE
从表loans
中获取Uniq_ID
相同年份但上个月的值,然后将其与当前行BALANCE
值进行比较。该fdate
列看起来像3/1/2019
。我尝试按以下方式进行操作,但出现错误"Sybase Database Error: Feature, reference containing a scalar value subquery (defined at line 13) inside a conditional expression (CASE, COALESCE, ARGN, NULLIF, or IF), is not supported"
。我该如何尝试以另一种方式做到这一点?
SELECT h.UNIQUEID, f.num
(select BALANCE from loans b
where b.UNIQ_ID = h.UNIQ_ID
and year(b.FDATE) = year(h.FDATE)
and MONTH(b.fdate) = MONTH(h.fdate) - 1) AS prev_bal,
(case when prev_bal > 0 and prev_bal >= BALANCE then 1 else 0 end) as flag
FROM loans h, perform f
where f.uniq_id = h.uniq_id
编辑:
数据如下所示:
fdate UNIQUEID NUM BALANCE
3/1/2019 LNSAR17224-00453434 1 16254.1
4/1/2019 LNSAR17224-00453434 1 15643.2
我想添加prev_bal
如下所示的列:
fdate UNIQUEID NUM BALANCE prev_bal
3/1/2019 LNSAR17224-00453434 1 16254.1 {null}
4/1/2019 LNSAR17224-00453434 1 15643.2 16254.1
预期输出:
UNIQUEID NUM prev_bal flag
LNSAR17224-00453434 1 {null} 0
LNSAR17224-00453434 1 16254.1 1
解决方案
假设:
- 数据库配置为不区分大小写(否则 OP 可以根据需要进行编辑以将所有列引用设置为上()或下())
- 该
perform
表有 2x 列命名uniq_id
和UNIQUEID
(否则 OP 可以解决拼写错误) - 由
previous month
OP 引用当前月份之前的最后一个条目(即,不一定是上一个日历月);所以这意味着我们可以利用该max()
函数来查找previous month
[替代方法是查找上一个日历月的匹配项,如果不存在则视为外连接;当然可以编码,但会等待 OP 输入] - OP 显示了一个输出记录的
NULL
值;prev_balance
我认为这意味着可能没有任何previous month
数据(即,我们需要考虑使用外连接)
一个(我相信)解决上述问题的查询:
select h.UNIQUEID,
f.num,
d1.prev_balance,
isnull(d1.flag,0) as flag
from loans h
join perform f
on f.uniq_id = h.uniq_id
left
join (select h2.UNIQ_ID, -- data associated with previous date
h2.BALANCE as prev_balance,
case when h2.BALANCE > 0 and h2.BALANCE >= h.BALANCE
then 1
else 0
end as flag
from loans h2
where h2.UNIQ_ID = h.UNIQ_ID
and h2.FDATE = (select max(h3.FDATE) as prev_fdate -- find previous date
from loans h3
where h3.UNIQ_ID = h2.UNIQ_ID
and h3.FDATE < h2.FDATE)
) as d1
on h.uniq_id = d1.uniq_id
或摆脱一级子查询:
select h.UNIQUEID,
f.num,
h2.BALANCE as prev_balance,
isnull(case when h2.BALANCE > 0 and h2.BALANCE >= h.BALANCE
then 1
else 0
end,0) as flag
from loans h
join perform f
on h.uniq_id = f.uniq_id
left
join loans h2
on h.uniq_id = h2.uniq_id
and h2.FDATE = (select max(h3.FDATE) as prev_fdate -- find previous date
from loans h3
where h3.UNIQ_ID = h2.UNIQ_ID
and h3.FDATE < h2.FDATE)
注意:没有表 DDL 或示例数据,因此目前无法测试上述语法/数据准确性......