1、相当与mysql的show databases;

select datname from pg_database;

2、相当于mysql的show tables;

SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';

public 是默认的schema的名字

3、相当与mysql的describe table_name;

SELECT column_name FROM information_schema.columns WHERE table_name ='table_name';

'table_name'是要查询的表的名字