如何檢查兩個日期是否在SQL存儲過程的某個日期範圍內？

Question

這裏是我的存儲過程：

ALTER Procedure [dbo].[SearchCreatedAssignments] 
(@LessonName NVarchar(MAX), @DateFrom date, @DateTo Date, @LocationCode NVarchar(MAX)) 
As 
BEGIN 
Select * 
from dbo.CreatedAssignments 
--IsNull replaces NULL with the specified replacement value. 
--IsNull(check_expression, replacement_value) 
--NullIf returns a null value if the two specified expressions are equal. 
--In other words, NULLIF returns the first expression if the two expressions are not equal. 
--If the expressions are equal, NULLIF returns a null value of the type of the first expression. 

where LessonName = IsNull(NullIf(@LessonName,''),LessonName) 
AND StartDate = IsNull(NullIf(@DateFrom,''),StartDate) 
AND EndDate  = IsNull(NullIf(@DateTo,''),EndDate) 
AND LocationCode = IsNull(NullIf(@LocationCode,''),LocationCode) 
AND status ='a' 

END 

正如你所看到的，此存儲過程設置，使用戶可以通過任何一個搜索標準，或者搜索條件的任意組合進行搜索（條件是列名），而將其他標準留空。例如，假設用戶只想通過lessonname搜索數據庫。這個存儲過程允許用戶做到這一點。它將返回與指定的lessonname匹配的所有結果，而不管其他條件是否保留爲空。所以，這裏是我的問題：我怎麼能保留這個邏輯，但返回的結果在哪裏的日期範圍內的startdate和enddate？我知道我需要使用between關鍵字，但我不確定如何實現這一更改，同時保留現有的邏輯。任何幫助是極大的讚賞。

Answer 1

如果你想要的開始日期和結束日期落在相同日期範圍內 - 即你@DateFrom和@DateTo參數 - 你可以做這樣的：

ALTER Procedure [dbo].[SearchCreatedAssignments] 
(@LessonName NVarchar(MAX), @DateFrom date, @DateTo Date, @LocationCode 
NVarchar(MAX)) 
As 
BEGIN 
Select * 
from dbo.CreatedAssignments 
--IsNull replaces NULL with the specified replacement value. 
--IsNull(check_expression, replacement_value) 
--NullIf returns a null value if the two specified expressions are equal. 
--In other words, NULLIF returns the first expression if the two expressions  are not equal. 
--If the expressions are equal, NULLIF returns a null value of the type of  the first expression. 

where LessonName = IsNull(NullIf(@LessonName,''),LessonName) 
AND StartDate BETWEEN IsNull(NullIf(@DateFrom,''),'1901-01-01') AND IsNull(NullIf(@DateTo,''),'2199-01-01') 
AND EndDate  BETWEEN IsNull(NullIf(@DateFrom,''),'1901-01-01') AND IsNull(NullIf(@DateTo,''),'2199-01-01') 
AND LocationCode = IsNull(NullIf(@LocationCode,''),LocationCode) 
AND status ='a' 

END 

請注意，我將您的IsNulls的第二個參數更改爲使用標量值而非實際列。我這樣做是爲了防止當一個日期參數保留空白時出現問題，這可能會給您提供錯誤順序的比較日期（例如StartDate BETWEEN 1/1/2017和1/1/2015）。

Answer 2

您可以在每個字段之間的運算符之間使用。

ALTER Procedure [dbo].[SearchCreatedAssignments] 
(@LessonName NVarchar(MAX), @DateFrom date, @DateTo Date, @LocationCode NVarchar(MAX)) 
As 
BEGIN 
Select * 
from dbo.CreatedAssignments 
--IsNull replaces NULL with the specified replacement value. 
--IsNull(check_expression, replacement_value) 
--NullIf returns a null value if the two specified expressions are equal. 
--In other words, NULLIF returns the first expression if the two expressions are not equal. 
--If the expressions are equal, NULLIF returns a null value of the type of the first expression. 

where LessonName = IsNull(NullIf(@LessonName,''),LessonName) 
AND (StartDate BETWEEN @DateFrom AND @DateTo) AND 
AND (EndDate BETWEEN @DateFrom AND @DateTo) AND 
AND LocationCode = IsNull(NullIf(@LocationCode,''),LocationCode) 
AND status ='a' 

END