登录：
psql -U ${USERNAME} -W
1、列举数据库：\l
2、选择数据库：\c 数据库名
3、查看该某个库中的所有表：\dt
4、切换数据库：\c interface
5、查看某个库中的某个表结构：\d 表名
6、查看某个库中某个表的记录：select * from apps limit 1;
7、显示字符集：\encoding
8、退出psgl：\q
查看每个库的大小：
select pg_database.datname as dbname,
pg_database_size(pg_database.datname) AS size1,
pg_size_pretty(pg_database_size(pg_database.datname)) as size2
from pg_database;
查看每个表的大小:
select relname, pg_size_pretty(pg_relation_size(relid)) from pg_stat_user_tables where schemaname='public' order by pg_relation_size(relid) desc;
