使用concat做字符串拼接和数据迁移

作用:

  解决一开始数据库建立不合理造成的字段冗余,从而提取部分字段,数据迁移、拼接字符串的功能。

格式:

  concat(字段1,'间隔符',字段2....)

  concat_ws('间隔符',字段1,字段2)

数据准备:

  

#创建表
create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum('male','female') not null default 'male', #大部分是男的
age int(3) unsigned not null default 28,
hire_date date not null,
post varchar(50),
post_comment varchar(100),
salary double(15,2),
office int, #一个部门一个屋子
depart_id int
);
#插入记录
#三个部门:教学,销售,运营
insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部
('alex','male',78,'20150302','teacher',1000000.31,401,1),
('wupeiqi','male',81,'20130305','teacher',8300,401,1),
('yuanhao','male',73,'20140701','teacher',3500,401,1),
('liwenzhou','male',28,'20121101','teacher',2100,401,1),
('jingliyang','female',18,'20110211','teacher',9000,401,1),
('jinxin','male',18,'19000301','teacher',30000,401,1),
('成龙','male',48,'20101111','teacher',10000,401,1),

('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
('丫丫','female',38,'20101101','sale',2000.35,402,2),
('丁丁','female',18,'20110312','sale',1000.37,402,2),
('星星','female',18,'20160513','sale',3000.29,402,2),
('格格','female',28,'20170127','sale',4000.33,402,2),

('张野','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门
('程咬金','male',18,'19970312','operation',20000,403,3),
('程咬银','female',18,'20130311','operation',19000,403,3),
('程咬铜','male',18,'20150411','operation',18000,403,3),
('程咬铁','female',18,'20140512','operation',17000,403,3)
;

  操作示例:

  只做字符串的拼接:

 1 mysql> select concat('name:',name) as mingzi,concat('sex:',sex) from  emp;
 2 +-----------------+--------------------+
 3 | mingzi          | concat('sex:',sex) |
 4 +-----------------+--------------------+
 5 | name:egon       | sex:male           |
 6 | name:alex       | sex:male           |
 7 | name:wupeiqi    | sex:male           |
 8 | name:yuanhao    | sex:male           |
 9 | name:liwenzhou  | sex:male           |
10 | name:jingliyang | sex:female         |
11 | name:jinxin     | sex:male           |
12 | name:成龙       | sex:male           |
13 | name:歪歪       | sex:female         |
14 | name:丫丫       | sex:female         |
15 | name:丁丁       | sex:female         |
16 | name:星星       | sex:female         |
17 | name:格格       | sex:female         |
18 | name:张野       | sex:male           |
19 | name:程咬金     | sex:male           |
20 | name:程咬银     | sex:female         |
21 | name:程咬铜     | sex:male           |
22 | name:程咬铁     | sex:female         |
23 +-----------------+--------------------+
24 18 rows in set (0.00 sec)

  数据迁移(同时进行字符串拼接):

 1 mysql> create table aa select concat('name:',name) as mingzi,concat('sex:',sex) from  emp;
 2 Query OK, 18 rows affected (0.03 sec)
 3 Records: 18  Duplicates: 0  Warnings: 0
 4 
 5 mysql>
 6 mysql> show tables;
 7 +---------------+
 8 | Tables_in_db2 |
 9 +---------------+
10 | aa            |
11 | big_data      |
12 | emp           |
13 +---------------+
14 3 rows in set (0.00 sec)
15 
16 mysql> select * from aa ;
17 +-----------------+--------------------+
18 | mingzi          | concat('sex:',sex) |
19 +-----------------+--------------------+
20 | name:egon       | sex:male           |
21 | name:alex       | sex:male           |
22 | name:wupeiqi    | sex:male           |
23 | name:yuanhao    | sex:male           |
24 | name:liwenzhou  | sex:male           |
25 | name:jingliyang | sex:female         |
26 | name:jinxin     | sex:male           |
27 | name:成龙       | sex:male           |
28 | name:歪歪       | sex:female         |
29 | name:丫丫       | sex:female         |
30 | name:丁丁       | sex:female         |
31 | name:星星       | sex:female         |
32 | name:格格       | sex:female         |
33 | name:张野       | sex:male           |
34 | name:程咬金     | sex:male           |
35 | name:程咬银     | sex:female         |
36 | name:程咬铜     | sex:male           |
37 | name:程咬铁     | sex:female         |
38 +-----------------+--------------------+
39 18 rows in set (0.00 sec)
原文地址:https://www.cnblogs.com/liuyinzhou/p/8058134.html