postgres=# create database mydb; CREATE DATABASE postgres=# alter database mydb; ALTER DATABASE postgres=# create table mydbtable(name varchar(80),year int); CREATE TABLE postgres=# create table mydbtable(name varchar(80),year int); ERROR: relation "mydbtable" already exists postgres=# insert into mydbtable (name,year) values ('xiaoming',23); INSERT 0 1 postgres=# table mydbtable; name | year ----------+------ xiaoming | 23 (1 row) postgres=# select * from mydbtable; name | year ----------+------ xiaoming | 23 (1 row) postgres=# select name from mydbtable; name ---------- xiaoming (1 row) postgres=# insert into mydbtable (name,year) values ('xiaohong',23); INSERT 0 1 postgres=# select name from mydbtable; name ---------- xiaoming xiaohong (2 rows) postgres=# update mydbtable set name = 'xiaohei' where name='xiaohong'; UPDATE 1 postgres=# select name from mydbtable; name ---------- xiaoming xiaohei (2 rows) postgres=# postgres=# delete from mydbtable where name='xiaohei'; DELETE 1 postgres=# select name from mydbtable; name ---------- xiaoming (1 row) postgres=# delete from mydbtable; DELETE 1 postgres=# select * from mydbtable; name | year ------+------ (0 rows) postgres=# postgres=# create database testdb; CREATE DATABASE postgres=# alter database testdb; ALTER DATABASE