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)