PostgreSQL 序列(Sequence) 基本操作 --新增序列CREATESEQUENCE xxx_id_seq INCREMENT1-- 一次加多少 MINVALUE 1 -- 最小值 START 1 --从多少开始 CACHE 1 CYCLE;--指定表使用altertablexxx_tablealtercolumnidsetDEFAULTnextval('xxx_id_seq')--查询序
1) Creating an ascending sequence example This statement uses theCREATE SEQUENCEstatement to create a new ascending sequence starting from 100 with an increment of 5: CREATESEQUENCEmysequenceINCREMENT5START100; To get the next value from the sequence, you use thenextval()function: ...
Example 3: Accessing the Sequence Code: -- Get the next value in the sequence SELECT nextval('employees_emp_id_seq'); -- Set the sequence to a specific value SELECT setval('employees_emp_id_seq', 100); -- Check the current value of the sequence SELECT currval('employees_emp_id_seq'...
Removing the MAXVALUE option from the sequence will set the maximum value to the default(i.e. Default maximum value of the specified data type). ALTERSEQUENCEexample_seqNOMAXVALUE; In this case, the stated error wouldn’t appear until the sequence reaches the maximum value of the specif...
Use DROP SEQUENCE to remove a sequence.Examples:Create an ascending sequence called idno, starting at 50:Code:postgres=# CREATE SEQUENCE idno START 50; CREATE SEQUENCE postgres=# CopySelect the next number from this sequence:Output:postgres=# SELECT nextval('idno'); nextval --- 50 (1 row...
An example of how to Create Sequence in PostgreSQL CREATE SEQUENCE phonebook_id_seq; CREATE TABLE phonebook(id INTEGER DEFAULT NEXTVAL('phonebook_id_seq'), phone VARCHAR(32), firstname VARCHAR(32), lastname VARCHAR(32)); INSERT INTO phonebook(phone, firstname, lastname) VALUES('+1 123 456...
PostgreSQL主要通过序列(sequence)和`SERIAL`类型来实现类似自增的效果。 ### 关键词 PostgreSQL, 主键, 自增, 序列, SERIAL ## 一、主键自增概念解析 ### 1.1 PostgreSQL与MySQL主键自增的对比分析 在数据库设计中,主键自增是一个常见的需求,它能够确保每条记录都有一个唯一的标识符。MySQL和PostgreSQL作为两...
NOTICE: CREATE TABLE will create implicit sequence "t_kenyon_id_seq" for serial column "t_kenyon.id" NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t_kenyon_pkey" for table "t_kenyon" CREATE TABLE postgres=# \d+ t_kenyon ...
2、serial8类型,,自动创建一个序列,同时将列设置为INT8,默认值设置为nextval('序列')。 create table test(id serial8, info text); 3、序列+默认值设置为序列, create sequence seq1; create table test (id int default nextval('seq1'), info text); 为了兼容SQL Server或SQL标准,PostgreSQL 10加入...
select nextval('t_a_seq'::regclass);ALTER SEQUENCE name [ INCREMENT [ BY ] increment ] [ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ] [ START [ WITH ] start ] [ RESTART [ [ WITH ] restart ] ]