-- SQL示例
SELECT 
    CASE 
        WHEN (A.start_date IS NULL OR B.end_date IS NULL OR A.start_date <= B.end_date) 
         AND (A.end_date IS NULL OR B.start_date IS NULL OR A.end_date >= B.start_date)
        THEN '重叠'
        ELSE '不重叠'
    END AS overlap_status
FROM date_ranges A, date_ranges B
WHERE A.id != B.id;

# Python示例
def is_overlap(range1, range2):
    start1, end1 = range1
    start2, end2 = range2
    
    # 处理null/None情况
    if start1 is None and end1 is None:
        return True  # 无限范围与任何范围都重叠
    if start2 is None and end2 is None:
        return True
    
    # 检查重叠条件
    no_overlap = (
        (end1 is not None and start2 is not None and end1 < start2) or
        (end2 is not None and start1 is not None and end2 < start1)
    )
    return not no_overlap