根据所选月份从表格中获取月份

Question

我试图获取患者部门和月份明智的报告。我正在选择一个部门和这个月份。我怎样才能明智地获得选定的月份记录部门。我想下面的查询，但不工作：

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

Answer 1

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

SQLFIDDLE
此外，我发现similar question在那里你可以得到这个线程额外的解决方法以及other answer。

Answer 2

如果你想单月/年对下面的查询将工作：

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

它查询可以使用索引，因为它并不需要在每一行进行计算的优势。

在查询之前计算限制通常是有帮助的，例如，当月：

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：如果使用比较操作的布尔运算符放在一起不管三七二十一是压倒性的，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; 

没有，IN不在documentation中列为比较运算符。