Question

我有一张桌子

Date,       employee    transaction  amount 
02-03-2015    e1          credit      400
02-03-2015    e1          debit        25
02-04-2015    e2          credit      600
02-04-2015    e2          debit        35
02-03-2015    e1          credit      400
02-03-2015    e1          debit       250

我想创建一个临时表，如下所示：

Date,       employee    transaction  amount 
02-03-2015    e1          credit      400
02-03-2015    e1          debit        25
02-03-2015    e1          NET_BAL     375
02-04-2015    e2          credit      600
02-04-2015    e2          debit        35
02-04-2015    e2          NET_BAL     565
02-04-2015    e1          credit      400
02-04-2015    e1          debit       250
02-04-2015    e1          NET_BAL     150

有人可以帮忙吗？我是SQL新手

Answer 1

这是你 CAN 这样做的方式，而不是你应该如何做到这一点。甚至PostgreSQL（或其他几个RDBMS系统）也可以操作数据来呈现非规范化和异构结果，表示层应该负责从服务器获取数据并将其分解并格式化，而不是数据库服务器。

with
  data (date, employee, transaction, amount) as (values
    ('02-03-2015', 'e1', 'credit', 400),
    ('02-03-2015', 'e1', 'debit', 25),
    ('02-04-2015', 'e2', 'credit', 600),
    ('02-04-2015', 'e2', 'debit', 35),
    ('02-04-2015', 'e1', 'credit', 400),
    ('02-04-2015', 'e1', 'debit', 250)),
  net as (
    select date, employee, 'NET_BAL'::text as transaction, sum(case when transaction = 'debit' then -1 else 1 end * amount) as amount
    from data
    group by date, employee)

select * from data
union
select * from net
order by date, employee, transaction

PostgreSQL：作为新行的2行的差异

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