sql-server - 根据所选月份从表中获取月份

Question

我正在尝试获取患者部门和每月明智的报告。我正在选择一个部门和月份。我怎样才能明智地只获得选定月份的记录部门。我正在尝试以下查询但不工作：

SELECT MONTH(select convert(varchar,creation_Date,105) from Patient_Ref_master)

Answer 1

如果您想要一个月/年对，则以下查询将起作用：

select *
  from Patient_Ref_Master
  where Cast( '20130801' as Date ) <= Creation_Date and Creation_Date < Cast( '20130901' as Date )

它的优点是查询可以使用索引，因为它不需要对每一行执行计算。

在查询之前计算限制通常很有帮助，例如当前月份：

declare @Start as Date = DateAdd( month, DateDiff( month, 0, GetDate() ), 0 );
declare @End as Date = DateAdd( month, 1, @Start );
select *
  from Patient_Ref_Master
  where @Start <= Creation_Date and Creation_Date < @End

编辑：如果将比较运算符与布尔运算符一起使用是压倒性的，我提供以下简化：

declare @Patient_Ref_Master as Table ( Id Int Identity, Creation_Date Date );
insert into @Patient_Ref_Master ( Creation_Date ) values
  ( '20130731' ), ( '20130801' ), ( '20130815' ), ( '20130831' ), ( '20130901' );
select * from @Patient_Ref_Master;

declare @Start as Date = DateAdd( month, DateDiff( month, 0, Cast( '20130829' as Date ) ), 0 );
declare @End as Date = DateAdd( month, 1, @Start );

-- Incomprehensible   WHERE   clause:
select *
  from @Patient_Ref_Master
  where @Start <= Creation_Date and Creation_Date < @End;

-- Simplified AB version:
with
  JustRight as (
    select *
      from @Patient_Ref_Master
      where Creation_Date in ( @Start ) ),
  NotTooLate as (
    select *
      from @Patient_Ref_Master
      where Sign( DateDiff( day, @End, Creation_Date ) ) in ( -1 ) ),
  NotTooSoon as (
    select *
      from @Patient_Ref_Master
      -- NB: Do NOT include zero in the set of matches. That would be too easy.
      where Sign( DateDiff( day, Creation_Date, @Start ) ) in ( -1 ) ),
  TheResult as (
    select *
      from JustRight
    union
    select *
      from NotTooLate
    intersect
    select *
      from NotTooSoon )
  select * from TheResult;

不，文档IN中未将其列为比较运算符。

Answer 2

select * from Patient_Ref_master
where MONTH(creation_Date)=1 --target month here, JAN as example  

SQLFIDDLE
我还发现了类似的问题，您可以在此线程中获得额外的解决方法以及其他答案。