sql语句如何实现插入不重复的20位字符串(mysql)？

#md5截取15位

delimiter @

DROP PROCEDURE IF EXISTS insert_Table;

create procedure insert_Table(in item integer)

begin

declare counter int;

set counter = item;

while counter >= 0 do

insert into name(uid,name) values(counter, UPPER(concat('ABCDE',LEFT(md5(counter),15))) );

set counter = counter - 1;

end while;

end

@

delimiter @

call insert_Table(1000000);

@