1、查询数据库版本

     select version();

2、查询数据库的运行时间

     select current_timestamp-pg_postmaster_start_time() as uptime;

3、查询数据库的数据量

SELECT

    datname ,

    a.rolname ,

    pg_encoding_to_char(encoding) ,

    datcollate ,

    datctype ,

    pg_size_pretty(pg_database_size(datname))

FROM

    pg_database d ,

    pg_authid a

WHERE

    d.datdba = a.oid

    AND datname NOT IN ('template0' ,'template1' ,'postgres' )

ORDER BY

    pg_database_size(datname) DESC;

4、 查询数据库连接数使用情况

   SELECT

        s.setting "可用连接数"       ,

        a.used_session "已使用连接数" ,

        s.setting::bigint - a.used_session "剩余连接数"

FROM

        pg_settings s,

        (

                SELECT

                        COUNT(*) AS used_session

                FROM

                        pg_stat_activity) a

WHERE

        s.name='max_connections';

5、查询数据库参数配置

     select name,setting,unit  from pg_settings;

6、查询当前数据库

     select current_database();