postgreSQL自动生成随机数值的实例

create or replace function gen_id(  
 a date,  
 b date  
)   
returns text as $$  
select lpad((random()*99)::int::text, 2, '0') ||   
    lpad((random()*99)::int::text, 2, '0') ||   
    lpad((random()*99)::int::text, 2, '0') ||   
    to_char(a + (random()*(b-a))::int, 'yyyymmdd') ||   
    lpad((random()*99)::int::text, 2, '0') ||   
    random()::int ||   
    (case when random()*10 >9 then 'X' else (random()*9)::int::text end ) ;  
$$ language sql strict; 

select gen_id('1900-01-01', '2017-10-16') from generate_series(1,10); 

insert into testpg SELECT generate_series(1,100000) as xm, gen_id('1900-01-01', '2017-10-16') as num;

@Id
@GeneratedValue(generator="system_uuid")
@GenericGenerator(name="system_uuid",strategy="uuid")
@Column(name = "ID", unique = true, nullable = false, length = 24)
public String getId() {
  return this.id;
}