转载自:http://blog.csdn.net/desilting/article/details/38563087
Mysql的查询结果行字段拼接,可以用下面两个函数实现:
1. concat函数
- mysql> select concat('1','2','3') from test ;
- +---------------------+
- | concat('1','2','3') |
- +---------------------+
- | 123 |
- +---------------------+
- mysql> select concat('1','2',NULL,'3') from test ;
- +--------------------------+
- | concat('1','2',NULL,'3') |
- +--------------------------+
- | NULL |
- +--------------------------+
2. concat_ws函数
concat(separator,str1,str2,...) 代表 concat with separator ,是concat()的特殊形式。第一个参数是其它参数的分隔符。分隔符的位置放在要连接的两个字符串之间。分隔符可以是一个字符串,也可以是其它参数。
- mysql> select concat_ws(':','1','2','3') from test ;
- +----------------------------+
- | concat_ws(':','1','2','3') |
- +----------------------------+
- | 1:2:3 |
- +----------------------------+
- mysql> select concat_ws(NULL,'1','2','3') from test;
- +-----------------------------+
- | concat_ws(NULL,'1','2','3') |
- +-----------------------------+
- | NULL |
- +-----------------------------+
- mysql> select concat_ws(':','1','2',NULL,NULL,NULL,'3') from test ;
- +-------------------------------------------+
- | concat_ws(':','1','2',NULL,NULL,NULL,'3') |
- +-------------------------------------------+
- | 1:2:3 |
- +-------------------------------------------+
可以对NULL进行判断,并用其它值进行替换:
- mysql> select concat_ws(':','1','2',ifNULL(NULL,'0'),'3') from bank limit 1;
- +---------------------------------------------+
- | concat_ws(':','1','2',ifNULL(NULL,'0'),'3') |
- +---------------------------------------------+
- | 1:2:0:3 |
- +---------------------------------------------+