contact用法解析

经典用法:

mysql> select concat('11','22','33');
+------------------------+
| concat('11','22','33') |
+------------------------+
| 112233 |
+------------------------+
1 row in set (0.00 sec)

MySQL的concat函数在连接字符串的时候，只要其中一个是NULL,那么将返回NULL
mysql> select concat('11','22',null);
+------------------------+
| concat('11','22',null) |
+------------------------+
| NULL   |
+------------------------+
1 row in set (0.00 sec)

 实战演练：

SELECT eg.* FROM wanghaokuneg eg
WHERE CONCAT(eg.c,eg.e,eg.b) IN (6103)

表数据：
a   b   c   d   e   f       g
2   3   61  涤纶  0   0   0