Question

有没有办法将聚合SQL查询转换为MS Access SQL？

一个简单的例子：

表：

CREATE TABLE testing.testtable
(
  aid serial NOT NULL,
  username text,
  words integer,
  sys_time timestamp with time zone NOT NULL DEFAULT now(),
  CONSTRAINT testtable_pkey PRIMARY KEY (aid)
)

insert into testing.testtable (username, words) values
('bob', 30),
('todd', 20),
('bob', 50),
('todd', 10);

我想要转换为Access SQL的PostgreSQL语句：

with cur as
(
    select testtable.username, AVG(testtable.words) as avgwords
    from testing.testtable
    group by testtable.username
), 
prev as
(
    select testtable.username, AVG(testtable.words) as avgwords
    from testing.testtable
    where testtable.sys_time <  date_trunc('day', NOW() - interval '1 month')
    group by testtable.username
)
    select p.username, c.avgwords - p.avgwords as change
    from prev p, cur c
    where p.username = c.username

Answer 1

首先，我会使用条件聚合重写Postgres查询：

select tt.username,
       avg(tt.words) - avg(case when tt.sys_time <  date_trunc('day', NOW() - interval '1 month') then tt.words end)
from testing.testtable tt
group by tt.username

您可以在MS Access中执行几乎相同的操作。排序：

select tt.username,
       avg(tt.words) - avg(iif(tt.sys_time < dateadd("m", -1, date()), tt.words, NULL)
from testing.testtable as tt
group by tt.username;

我不认为MS Access会执行整数的整数平均值。如果是这样，您可能希望将words字段转换为avg()之前的小数值。

但是，我鼓励您继续使用Postgres。

有没有办法将PostgreSQL语句（聚合）转换为MS Access SQL？

1 个答案: