postgres 数据库
为已有的字段添加默认值
ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT default_value;
删除默认值
ALTER TABLE table_name ALTER COLUMN column_name DROP DEFAULT;
给postgre添加自增字段
方法一：
CREATE TABLE customers
(
customerid SERIAL primary key ,
companyname character varying,
contactname character varying,
phone character varying,
country character varying
)
方法二：
CREATE SEQUENCE event_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;
alter table event alter column id set default nextval('event_id_seq');
重置序列
ALTER SEQUENCE tab_seq RESTART WITH 1;
添加索引
单字段索引：
CREATE INDEX index_name ON table_name (field1);
联合索引：
CREATE INDEX index_name ON table_name (field1,field2);
数据之间导入导出
insert into chronic(name, attr, content )
select name, attr, content from disease where name = '高血脂'