Mysql查询选项参数

Question

有我的查询字符串，有没有关于bindParam的任何问题？

$str = "select A.option_id,count(*) as sum 
      from tb_feedback A,tb_question B,tb_group C 
      where (A.question_id=B.id) 
      and (:question is null or B.id=:question) 
      and (B.group_num=C.id) 
      and (:group is null or C.name=:group) 
      and (:fromdate is null or A.date >= CAST(:fromdate AS DATE)) 
      and (:todate is null or A.date <= CAST(:todate AS DATE)) 
      group by A.option_id"; 
     $sql = $this->conn->prepare($str); 
     $sql->bindParam(':question', $obj['question']); 
     $sql->bindParam(':group', $obj['group']); 
     $sql->bindParam(':fromdate', $obj['fromdate']); 
     $sql->bindParam(':todate', $obj['todate']); 

Answer 1

我发现，参数的类型不为空，它是字符串的原因，所以当执行下一条语句 (:question is null or B.id=:question)