${if(len(p_start) = 0 && len(p_end) = 0, " SUM( NVL(duration_real, 0)) as duration_real,", " SUM(case when trunc(record_time)>= TO_DATE ('" + p_start + "', 'YYYY-MM-DD')" + " and trunc(record_time)<= TO_DATE('" + p_end + "', 'YYYY-MM-DD') then NVL(duration_real, 0) else 0 end ) as duration_real ," ) }有大神可以可以解释一下这段SQL 是什么意思吗? 看不太懂。