mydb=# \l
                                    List of databases
      Name      |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
----------------+----------+----------+-------------+-------------+-----------------------
 mcu            | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 mydb           | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
                |          |          |             |             | postgres=CTc/postgres
 template1      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | postgres=CTc/postgres+
                |          |          |             |             | =c/postgres
 test           | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 tieba_20100706 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
(7 rows)

mydb=# \d
          List of relations
 Schema |   Name   | Type  |  Owner   
--------+----------+-------+----------
 public | capitals | table | postgres
 public | cities   | table | postgres
 public | weather  | table | postgres
(3 rows)

mydb=#

「\c 數據庫名」是打開指定的數據庫，相當於mysql裏面的use語句。