mysql更新拼接字符串 mysql字段拼接字符串

在Mysql 数据库中存在两种字符串连接操作.具体操作如下

一. 语法:

CONCAT(string1,string2,…)

   例1:

    

   例2:

    

  2. CONCAT_WS(separator,str1,str2,...)

concat_ws 代表 concat with separator,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。如果分隔符为 NULL，则结果为 NULL。函数会忽略任何分隔符参数后的 NULL 值。

     举例1:

mysql> select concat_ws('#','courseName=','NX',null) AS nx_courseName;
 +-----------------------+
 | nx_courseName |
 +-----------------------+
 | courseName=#NX|
 +-----------------------+
 1 row in set (0.00 sec)

    例2:

mysql> select concat_ws('null','courseName=','NX',null) AS nx_courseName;+-----------------------+
 | nx_courseName |
 +-----------------------+
 | NULL |
 +-----------------------+
 1 row in set (0.00 sec)

  

3. MySQL中group_concat函数
完整的语法如下：
group_concat([DISTINCT] 要连接的字段 [Order BY ASC/DESC 排序字段] [Separator '分隔符'])

基本查询

mysql> select * from stu1;
 +------+------+
 | id| name |
 +------+------+
 |1 | 10|
 |1 | 20|
 |1 | 20|
 |2 | 20|
 |3 | 200   |
 |3 | 500   |
 +------+------+

6 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，逗号分隔(默认)

mysql> select id,group_concat(name) from aa group by id;
 +------+--------------------+
 | id| group_concat(name) |
 +------+--------------------+
 |1 | 10,20,20|
 |2 | 20 |
 |3 | 200,500|
 +------+--------------------+
 3 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，分号分隔

mysql> select id,group_concat(name separator ';') from aa group by id;
 +------+----------------------------------+
 | id| group_concat(name separator ';') |
 +------+----------------------------------+
 |1 | 10;20;20 |
 |2 | 20|
 |3 | 200;500   |
 +------+----------------------------------+
 3 rows in set (0.00 sec)

以id分组，把去冗余的name字段的值打印在一行，

逗号分隔

mysql> select id,group_concat(distinct name) from aa group by id;
+------+-----------------------------+
| id| group_concat(distinct name) |
+------+-----------------------------+
|1 | 10,20|
|2 | 20   |
|3 | 200,500 |
+------+-----------------------------+
3 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，逗号分隔，以name排倒序

mysql> select id,group_concat(name order by name desc) from aa group by id;
+------+---------------------------------------+
| id| group_concat(name order by name desc) |
+------+---------------------------------------+
|1 | 20,20,10   |
|2 | 20|
|3 | 500,200|
+------+---------------------------------------+
3 rows in set (0.00 sec)

 

还有一个简单的连接方式为: ||

 

mysql> select *  from student;
 +----+------+-------+----------+------------+
 | id | age  | score | name     | birth      |
 +----+------+-------+----------+------------+
 |  1 |   23 |    78 | 李四     | 2017-10-10 |
 |  2 |   24 |    78 | zhangsan | 2017-10-10 |
 |  3 |   25 |    99 | 王五     | 2016-05-17 |
 +----+------+-------+----------+------------+
 3 rows in set (0.00 sec)

 mysql> select id+999,name,name+99,name+'999' from student;
 +--------+----------+---------+------------+
 | id+999 | name     | name+99 | name+'999' |
 +--------+----------+---------+------------+
 |   1000 | 李四     |      99 |        999 |
 |   1001 | zhangsan |      99 |        999 |
 |   1002 | 王五     |      99 |        999 |
 +--------+----------+---------+------------+
 3 rows in set, 6 warnings (0.00 sec)