请问各位老大，postgre数据库创建以后，是否不用授权用户就自动有对改数据库访问和建表的权限？

根据如下步骤，用户erp_etl创建以后就可以对数据库进行登陆和在public模式建表。

如果这样就能在数据库建表和删表等，那么官方给的如下数据库授权语句的作用是什么呢？

https://www.postgresql.org/docs/current/sql-grant.html

GRANT { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...] | ALL [ PRIVILEGES ] }
    ON DATABASE database_name [, ...]
    TO role_specification [, ...] [ WITH GRANT OPTION ]
    [ GRANTED BY role_specification ]

建库

postgres=# create database erp encoding 'UTF8' LC_COLLATE = 'en_US.utf8' LC_CTYPE = 'en_US.utf8' template template0;
CREATE DATABASE
postgres=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+------------+------------+-----------------------
erp | postgres | UTF8 | en_US.utf8 | en_US.utf8 |
postgres | postgres | UTF8 | C | C |
template0 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
template1 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
(4 rows)

建用户

postgres=# drop role erp_etl;
DROP ROLE
postgres=# create role erp_etl password 'Bigdata@123' login;
CREATE ROLE

登陆

[postgres@vm01 ~]$ psql -h 10.10.10.2 -U erp_etl -d erp -p 1921
Password for user erp_etl:
psql (12.18)
Type "help" for help.

erp=> \d
Did not find any relations.
erp=> \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+------------+------------+-----------------------
erp | postgres | UTF8 | en_US.utf8 | en_US.utf8 |
postgres | postgres | UTF8 | C | C |
template0 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
template1 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
(4 rows)