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、 查询手游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::bigintwww.diuxie.com - 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();

如何查询postgresql数量？