备注:测试数据库版本为MySQL 8.0

Table of Contents

一.需求

将全名转换为大写首字母缩写，比如下面的名字:

Stewie Griffin

要求返回如下结果

S.G

二.解决方案

需要注意的就是SQL并不像C或Python语言那样灵活，所以，创建一个通用的解决方案来处理所有格式的姓名对于SQL来说不是一件容易的事情。在这里所介绍的解决方案假定名字都是由名和姓，或是由名、中间名(中间名缩写)及姓组成。

代码:

-- 2个

select case

when cnt = 2 then

trim(trailing '.' from

concat_ws('.',

substr(substring_index(name,' ',1),1,1),

substr(name,

length(substring_index(name,' ',1))+2,1),

substr(substring_index(name,' ',-1),1,1),

'.'))

else

trim(trailing '.' from

concat_ws('.',

substr(substring_index(name,' ',1),1,1),

substr(substring_index(name,' ',-1),1,1)

))

end as initials

from (

select name,length(name) - length(replace(name,' ','')) as cnt

from (

select replace('Stewie Griffin','.','') as name

) y

) x;

-- 3个

select case

when cnt = 2 then

trim(trailing '.' from

concat_ws('.',

substr(substring_index(name,' ',1),1,1),

substr(name,

length(substring_index(name,' ',1))+2,1),

substr(substring_index(name,' ',-1),1,1),

'.'))

else

trim(trailing '.' from

concat_ws('.',

substr(substring_index(name,' ',1),1,1),

substr(substring_index(name,' ',-1),1,1)

))

end as initials

from (

select name,length(name) - length(replace(name,' ','')) as cnt

from (

select replace('Stewie Griffin Boy','.','') as name

) y

) x;

测试记录

mysql> -- 2个

mysql> select case

-> when cnt = 2 then

-> trim(trailing '.' from

-> concat_ws('.',

-> substr(substring_index(name,' ',1),1,1),

-> substr(name,

-> length(substring_index(name,' ',1))+2,1),

-> substr(substring_index(name,' ',-1),1,1),

-> '.'))

-> else

-> trim(trailing '.' from

-> concat_ws('.',

-> substr(substring_index(name,' ',1),1,1),

-> substr(substring_index(name,' ',-1),1,1)

-> ))

-> end as initials

-> from (

-> select name,length(name) - length(replace(name,' ','')) as cnt

-> from (

-> select replace('Stewie Griffin','.','') as name

-> ) y

-> ) x;

+----------+

| initials |

+----------+

| S.G |

+----------+

1 row in set (0.00 sec)

mysql>

mysql> -- 3个

mysql> select case

-> when cnt = 2 then

-> trim(trailing '.' from

-> concat_ws('.',

-> substr(substring_index(name,' ',1),1,1),

-> substr(name,

-> length(substring_index(name,' ',1))+2,1),

-> substr(substring_index(name,' ',-1),1,1),

-> '.'))

-> else

-> trim(trailing '.' from

-> concat_ws('.',

-> substr(substring_index(name,' ',1),1,1),

-> substr(substring_index(name,' ',-1),1,1)

-> ))

-> end as initials

-> from (

-> select name,length(name) - length(replace(name,' ','')) as cnt

-> from (

-> select replace('Stewie Griffin Boy','.','') as name

-> ) y

-> ) x;

+----------+

| initials |

+----------+

| S.G.B |

+----------+

1 row in set (0.00 sec)

看到这一长串是不是很迷糊，我们把sql代码拆开来

-- 如果名称里面存在 '.' 替换为空

mysql> select replace('Stewie Griffin','.','') as name;

+----------------+

| name |

+----------------+

| Stewie Griffin |

+----------------+

1 row in set (0.00 sec)

-- 判断是 名和姓，或是由名、中间名(中间名缩写)及姓

mysql> select name,length(name) - length(replace(name,' ','')) as cnt

-> from (

-> select replace('Stewie Griffin','.','') as name

-> ) y;

+----------------+------+

| name | cnt |

+----------------+------+

| Stewie Griffin | 1 |

+----------------+------+

1 row in set (0.00 sec)

mysql> -- 通过substring截取' '第一次出现的地方，保留左边的

mysql> select substring_index('Stewie Griffin',' ',1) as n1;

+--------+

| n1 |

+--------+

| Stewie |

+--------+

1 row in set (0.00 sec)

mysql>

mysql> -- 截取第一个大写的字母

mysql> select substr('Stewie',1,1) as n2;

+------+

| n2 |

+------+

| S |

+------+

1 row in set (0.00 sec)

mysql>

mysql> -- 联合起来就是这样的

mysql> select substr(substring_index('Stewie Griffin',' ',1),1,1) as n1;

+------+

| n1 |

+------+

| S |

+------+

1 row in set (0.00 sec)

mysql>

mysql>

mysql>

mysql> -- 通过substring ' '最后一次出现的地方，保留右边的

mysql> select substring_index('Stewie Griffin',' ',-1) as n1;

+---------+

| n1 |

+---------+

| Griffin |

+---------+

1 row in set (0.00 sec)

mysql>

mysql> -- 截取第一个大写的字母

mysql> select substr('Griffin',1,1) as n2;

+------+

| n2 |

+------+

| G |

+------+

1 row in set (0.00 sec)

mysql>

mysql> -- 联合起来就是这样的

mysql> select substr(substring_index('Stewie Griffin',' ',-1),1,1) as n1;

+------+

| n1 |

+------+

| G |

+------+

1 row in set (0.00 sec)

mysql>

mysql>

-- trim 去掉最后面的'.'如存在

mysql> select trim(trailing '.' from 'S.G') as str;

+------+

| str |

+------+

| S.G |

+------+

1 row in set (0.00 sec)

mysql> select trim(trailing '.' from 'S.G.') as str;

+------+

| str |

+------+

| S.G |

+------+

1 row in set (0.00 sec)

mysql> select trim(trailing '.' from '.S.G.') as str;

+------+

| str |

+------+

| .S.G |

+------+

1 row in set (0.00 sec)

三.使用MySQL函数

代码:

-- 用函数进行封装

CREATE FUNCTION `f_get_name`(`pi_str` varchar(200)) RETURNS varchar(200) CHARSET utf8mb4

DETERMINISTIC

BEGIN

#Routine body goes here...

declare o_name varchar(200) default null;

declare l_cnt int default null;

declare o_name1 varchar(200) default null;

declare o_name2 varchar(200) default null;

declare o_name3 varchar(200) default null;

SELECT length(pi_str) - length(replace(pi_str,' ',''))

into l_cnt;

if l_cnt = 1 then

SELECT substr(substring_index(pi_str,' ',1),1,1)

into o_name1;

SELECT substr(substring_index(pi_str,' ',-1),1,1)

into o_name2;

SELECT concat(o_name1,'.',o_name2)

into o_name;

elseif l_cnt = 2 THEN

SELECT substr(substring_index(pi_str,' ',1),1,1)

into o_name1;

SELECT substr(pi_str,length(substring_index(pi_str,' ',1)) + 2,1)

into o_name2;

SELECT substr(substring_index(pi_str,' ',-1),1,1)

into o_name3;

SELECT concat(o_name1,'.',o_name2,'.',o_name3)

into o_name;

else

BEGIN

end;

end if;

RETURN o_name;

END

函数封装后，SQL代码真的简单太多

mysql> select f_get_name('Stewie Griffin') as name;

+------+

| name |

+------+

| S.G |

+------+

1 row in set, 1 warning (0.00 sec)

mysql> select f_get_name('Stewie Griffin Boy') as name;

+-------+

| name |

+-------+

| S.G.B |

+-------+

1 row in set (0.00 sec)