BETWEEN @Start and @End Date; Not pulling in records which fall beyond the date

Question

Currently working on a t-sql query which is supposed to get a list of all records that fall between the current fiscal year (we use 4-4-5 calendar). The record's start and end date are 06/02/2018, 31/07/2020.

The date I am filtering for is:

DECLARE @StartDate DATE = '12-29-2018';
DECLARE @EndDate DATE = '12-31-2019'; 

The condition I have in my where clause is:

 AND
          (

          (o.Revenue_Start_Date__c >= @StartDate AND  o.Revenue_End_Date__c <= @EndDate) OR (o.Revenue_End_Date__c >= @StartDate AND  o.Revenue_End_Date__c <= @EndDate)
          )

I have tried variations of BETWEEN as well. Any idea what I may be doing wrong and how do I get a list of all records to be included if it falls within the coresponding dates.

ANSWER:

AND  (  -- Starts Within range
  ( o.Revenue_Start_Date__c 
    BETWEEN @StartDate
    AND     @EndDate
  )
OR  -- Ends within range
  (
    o.Revenue_End_Date__c
    BETWEEN @StartDate
    AND     @EndDate
   )
OR    -- SPANS Range
   (
     o.Revenue_Start_Date__c < @StartDate
     AND
     o.Revenue_End_Date__c > @EndDate  
    )
    )

This seems to be working for me just now.

Answer 1

For fall through cases, this should work.

o.Revenue_Start_Date__c <= @EndDate AND o.Revenue_End_Date__c >= @StartDate

Answer 2

Is this what you want?

(o.Revenue_Start_Date__c < @EndDate AND 
 o.Revenue_End_Date__c >= @StartDate
)

This is the logic for overlapping intervals. Note that the inequalities might be exact or inexact depending on your actual definitions of overlapping.