KingbaseES 自增列三種方式

KingbaseES中3種自增長類型sequence，serial，identity的區別：

對象	顯示插入	顯示插入后更新最大值	清空表后是否重置	是否跟事務一起回滾	多對象共享	支持重置	出現錯誤后序列值是否增長
sequence	是	否	否	否	是	是	是
serial	是	否	否	否	否	是	是
identity	是	否	否	否	否	是	是

1、Sequence

create sequence seq_1 INCREMENT BY 1 MINVALUE 1 START WITH 1;
create table test_seq
(
    id int not null default nextval('seq_1') primary key,
    name varchar(10)
);

隱式插入
insert into test_seq (name) values ('aaa');
insert into test_seq (name) values ('bbb');
insert into test_seq (name) values ('ccc');

顯式插入
insert into  test_seq (id,name) values (5,'ddd');

再次隱式插入
test1=# insert into test_seq (name) values ('eee');
INSERT 0 1
test1=# insert into test_seq (name) values ('fff');
錯誤: 重復鍵違反唯一約束"test_seq_pkey"
描述: 鍵值"(id)=(5)" 已經存在

再次執行語句可正常插入，序列因為之前的錯誤調用自動增加
test1=# insert into test_seq (name) values ('fff');
INSERT 0 1

重置序列

--重置序列的最大值
select setval('seq_1',(select max(id) from  test_seq)::BIGINT);

--事務回滾后，序列號並不會回滾
test1=# begin;
BEGIN
test1=# insert into  test_seq (name) values ('ggg');
INSERT 0 1
test1=# rollback;
ROLLBACK

-- truncate 表之后，序列不受影響
test1=# truncate table  test_seq;
TRUNCATE TABLE
test1=# insert into  test_seq (name) values ('ggg');
INSERT 0 1
test1=#  select * from test_seq;
 id | name 
----+------
  9 | ggg
(1 行記錄)

--重置序列
ALTER SEQUENCE seq_1 RESTART WITH 1;
test1=# ALTER SEQUENCE  seq_1 RESTART WITH 1;
ALTER SEQUENCE
test1=# insert into  test_seq (name) values ('ggg');
INSERT 0 1
test1=#  select * from test_seq;                    
 id | name 
----+------
  9 | ggg
  1 | ggg

　　

2、Serial

create table  test_serial
(
    id serial primary key,
    name varchar(100)
);
隱式插入
insert into   test_serial(name) values ('aaa');
insert into   test_serial(name) values ('bbb');
insert into   test_serial(name) values ('ccc');
顯示插入
insert into   test_serial(id,name) values (5,'ddd);
select * from  test_serial;

--再次隱式插入,第二次會報錯
test1=# insert into   test_serial(id,name) values (5,'ddd);
INSERT 0 1
test1=# insert into   test_serial(name) values ('eee');
INSERT 0 1
test1=# insert into   test_serial(name) values ('fff');
錯誤:  重復鍵違反唯一約束"test_serial_pkey"
描述:  鍵值"(id)=(5)" 已經存在

--再次執行語句可正常插入，序列因為之前的錯誤調用自動增加
test1=# insert into test_serial(name) values ('fff');
INSERT 0 1

--重置serial
SELECT SETVAL((SELECT sys_get_serial_sequence(' test_serial', 'id')), 1, false);

　　

3、Identity

Identity是R6版本新增的語法，R3數據庫不支持該語法。

identity定義成generated by default as identity允許顯式插入，

identity定義成always as identity 不允許顯示插入，但是加上overriding system value也可以顯式插入。

create table  test_identiy_1 
(
    id int generated always as identity (START WITH 1 INCREMENT BY 1)  primary key , 
    name varchar(100)
);
insert into  test_identiy_1(name) values ('aaa');
insert into  test_identiy_1(name) values ('bbb');
insert into  test_identiy_1(name) values ('ccc');

--顯式插入值
如果定義為generated always as identity則不允許顯式插入，除非增加overriding system value 提示。
test1=# insert into test_identiy_1(id,name) values (5,'ccc');
錯誤:  無法插入到列"id"
描述:  列"id"是定義為GENERATED ALWAYS的標識列.
提示:  使用OVERRIDING SYSTEM VALUE覆蓋.
test1=# insert into test_identiy_1(id,name)overriding system value values (5,'ccc');
INSERT 0 1

 

generate by default:

create table  test_identiy_2
(
    id int generated by default as identity (START WITH 1 INCREMENT BY 1)  primary key , 
    name varchar(100)
);

insert into  test_identiy_2(name) values ('aaa');
insert into  test_identiy_2(name) values ('bbb');
insert into  test_identiy_2(name) values ('ccc');

test1=# insert into test_identiy_2(id,name) values (5,'ccc');
INSERT 0 1

 

重置 Identity　　

重置Identity的方式有2種：
1.	ALTER TABLE test_identiy_1 ALTER COLUMN id RESTART WITH 100;
2.	TRUNCATE table test_identiy_1 RESTART IDENTITY;