PostgreSQL 序列SEQUENCE

一、简介

序列对象（也叫序列生成器）就是用CREATE SEQUENCE 创建的特殊的单行表。一个序列对象通常用于为行或者表生成唯一的标识符。

二、创建序列

方法一：直接在表中指定字段类型为serial 类型

david=# create table tbl_xulie (
david(# id serial,david(# name text);
NOTICE:  CREATE TABLE will create implicit sequence "tbl_xulie_id_seq" for serial column "tbl_xulie.id"
TABLE
david=#

方法二：先创建序列名称，然后在新建的表中列属性指定序列就可以了，该列需int 类型

创建序列的语法：

CREATE [ TEMPORARY | TEMP ] SEQUENCE name  INCREMENT [ BY ] increment ]
     MINVALUE minvalue | NO MINVALUE ]  MAXVALUE maxvalue | NO MAXVALUE ]
     START [ WITH ] start ]  CACHE cache  [ NO  CYCLE ]
     OWNED BY { table.column | NONE } ]

实例：

create sequence tbl_xulie2_id_seq increment by 1 minvalue 1 no maxvalue start with 1; CREATE SEQUENCE david=#

tbl_xulie2 ( david(# id int4 not null default nextval('tbl_xulie2_id_seq'),0)">); =#

三、查看序列

david=# \d tbl_xulie
                         Table "public.tbl_xulie"
 Column |  Type   |                       Modifiers                        
--------+---------+--------------------------------------------------------
 id     | integer | tbl_xulie_id_seq::regclass)
 name   text     

david# \d tbl_xulie2
                         .tbl_xulie2"
                         Modifiers                        
------+---------+---------------------------------------------------------
 id     =#

查看序列属性

# \d tbl_xulie_id_seq Sequence ".tbl_xulie_id_seq" Column Value -------------+---------+--------------------- sequence_name | name tbl_xulie_id_seq last_value bigint start_value increment_by max_value 9223372036854775807 min_value cache_value log_cnt 0 is_cycled | boolean f is_called f Owned by: .tbl_xulie.id david