[我正在尝试在SQLServer Management Studio 2008中将一个查询放在一起,我通过'tax_id'将两个表联接在一起,但是我从表2(Tax_Rate_Table)中有一个重复的条目,我只需要在其中显示一个条目即可。您可以在下面看到最新的“有效日期”,Tax_ID 4具有重复的条目:
1.TAX_TABLE---------
tax_id description
1 AZ State
2 AZ-Maricopa Co
4 AZ-Maricopa/Mesa
2.Tax_RATE_TABLE-------
tax_id effective_date tax_percent
1 2015-01-01 00:00:00.000 5.6
2 2015-01-01 00:00:00.000 0.7
4 2015-01-01 00:00:00.000 1.75
4 2019-03-01 00:00:00.000 2
我按有效日期加入和降序有效,但是,我尝试使用“按有效日期降序限制1排序;”但是限制功能不起作用。
一个选项使用横向联接(不是SQL Server不支持limit
语法,而是使用top
):
select t.*, tr.effective_date, tr.tax_percent
from tax_table t
cross apply (
select top (1) *
from tax_rate_table tr
where tr.tax_id = t.tax_id
order by tr.effective_date desc
) tr
您也可以加入和过滤相关子查询:
select t.*, tr.effective_date, tr.tax_percent
from tax_table t
inner join tax_rate_table tr on tr.tax_id = t.tax_id
where tr.effective_date = (
select max(tr1.effective_date)
from tax_rate_table tr1
where tr1.tax_id = tr.tax_id
)
或者您可以使用row_number()
:
select *
from (
select
t.*,
tr.effective_date,
tr.tax_percent,
row_number() over(partition by t.tax_id order by tr.effective_date desc) rn
from tax_table t
inner join tax_rate_table tr on tr.tax_id = t.tax_id
) t
where rn = 1
;with rates
AS
(
SELECT *
,ROW_NUMBER() OVER (PARTITION BY tax_id ORDER BY effective_date desc) as pID
FROM tax_table t
inner join tax_rate_table r on t.ID = r.tax_id
)
select
tax_id
,DESCRIPTION
,effective_date
,percentage
FROM rates
WHERE pid = 1