SQL: Conditional Where Clause

If you have some scenario where you need to add where clause based on some condition.

for example:
GradeID     MinMark   MaxMark    Grade
1           0          0          A
2           0          10         B
3           11         20         C
4           21         NULL       D


As per above table we need Grade based on parameter @Mark to be checked as per the range of MinMark and MaxMark.
You can achive this by below query:

SELECT Grade
FROM Grades
Where
((MaxMark IS NULL AND MinMark<@Mark)
OR (MaxMark IS NOT NULL AND(@Mark BETWEEN MinMark AND MaxMark)))




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