How to avoid OR's(too many) in WHERE clause????

Question

I have similar code(below given is a sample prepared by me) in one of the existing SP.
dbo.[STUDENT] T1 INNER JOIN
dbo.[COLLEGE] T2 INNER JOIN
dbo.[DEPARTMENT] T3 INNER JOIN
dbo.[EXAM] T4 
WHERE T1.[student_id] = @student_id
AND (
(T1.[student_grade] = @GRADE_A)
OR
(T2.[college_location] = @COMP_CONTINENT_ASIA 
AND T2.[college_country_cde] IN ('AFG', 'ARM', 'BAN', 'CHI', 'IND', 'ISR', 'JAP'))
OR
(T2.[college_location] = @COMP_CONTINENT_AFRICA
AND T2.[college_country_cde] IN ('ALG', 'EGY', 'LIB', 'SUD', 'TUN', 'SOM'))
AND ( T3.[dept_id]  <> @DEPT_ID_COMP
 OR 
(T3.[dept_id]  = @DEPT_ID_COMP AND T4.[comp_exam_taken]  = 0))  
AND (T3.[dept_id] <> @DEPT_ID_ELECT
OR
(T3.[dept_id] = @DEPT_ID_ELECT AND T4.[elect_exam_taken]  = 0)))
AND ( T3.[dept_id] <> @DEPT_ID_MECH
OR
(T3.[dept_id]  = @DEPT_ID_MECH AND T4.[mech_exam_taken]  = 0 ))
AND ( T3.[dept_id] <> @DEPT_ID_CHEM
OR
(T3.[dept_id]  = @DEPT_ID_CHEM AND T4.[chem_exam_taken]  = 0 ))
AND ((T1.[student_status_cde] != @STU_STATUS_CODE_NEW) OR (T4.college_working_days IS NOT NULL AND T4.college_working_days > 90))
I tried to remove the OR's by using UNION, but it is leading to have number of(almost 96) UNIONs which would't be accepted.  Can someone suggest a better approach to avoid using OR's in WHERE condition?
Thanks in advance,
Ravi

Answer 1

Sometimes, business rules are complex, so there isn't always a way to simplify things.  Is your issue that it's complex and error prone, or is it performance due to the OR clauses?
One possibility that will at least make it easier to test and debug is something like this:  (pseudocode)
From Table1 Inner join Table2 on x=y etc.etc.
CROSS APPLY
(Select case when a=b and (c=d or e=f) then 1 else 0 end) as Situation1
, case when h=i or j = k then 1 else 0 end) as situation2
, case when l = m then 1 else 0 end) as situation 3
) as CA_Logic_Simplifier
Where situation1 = 1 and situation2 = 1 and situation3 = 1
Although you could say, "Hey, this is basically doing the same thing as before", this approach would be far easier to test and debug, because you can at a glance look at the values for situation1, 2, 3, etc. to see where errors are being introduced. 
The cross apply makes the columns situation1/2/3 "instantiated", so they are usable in the where clause. Divide and conquer.