我们如何克服 CONCAT() 函数的属性，即如果任何一个参数为 NULL，它就会返回 NULL，特别是当我们想要连接列中的值并且任何列的值都为 NULL 时？

Mysql> Select * from Student_Name;
+---------+-------+---------+
| FName   | Mname | Lname   |
+---------+-------+---------+
| Rahul   | NULL  | Singh   |
| Gaurav  | Kumar | NULL    |
| Harshit | NULL  | Khurana |
| Yash    | Pal   | Sharma  |
+---------+-------+---------+
4 rows in set (0.00 sec)

mysql> Select CONCAT(Fname,Mname,Lname)AS Name from Student_Name;
+---------------+
| Name          |
+---------------+
| NULL          |
| NULL          |
| NULL          |
| YashPalSharma |
+---------------+
4 rows in set (0.00 sec)

mysql> Select CONCAT(IFNULL(Fname,''),IFNULL(Mname,''),IFNULL(Lname,''))AS Name from Student_Name;
+----------------+
| Name           |
+----------------+
| RahulSingh     |
| GauravKumar    |
| HarshitKhurana |
| YashPalSharma  |
+----------------+
4 rows in set (0.06 sec)