mysql query 条件中为空时忽略

☆1.    q.ques_group传入为null或‘‘的时候不查询此条件：
          value = "SELECT *             FROM question q WHERE  1=1 AND (q.ques_group = :quesGroup or :quesGroup is null or :quesGroup=‘‘) AND q.type = :type",

        1： (q.ques_group = :quesGroup or :quesGroup is null or :quesGroup=‘‘)
        2： (q.ques_group = ISNULL(:quesGroup, q.ques_group) OR q.ques_group = (CASE WHEN :quesGroup = ‘‘ THEN q.ques_group ELSE :quesGroup END)) :分解：
            SELECT *             FROM question q WHERE  
            1=1 AND (q.ques_group = IFNULL(:quesGroup, q.ques_group) OR q.ques_group = (CASE WHEN :quesGroup = ‘‘ THEN q.ques_group ELSE :quesGroup END)) 
            AND q.type = :type",
        3：WHERE       (@AgentID=‘‘) OR (@AgentID<>‘‘ AND  A.AgentID = @AgentID)