详解PostgreSql数据库对象信息及应用

select * from information_schema.tables;
select * from pg_catalog.pg_tables;

select current_schema();

select * from information_schema.schemata;
select * from pg_catalog.pg_namespace

select current_database();

select * from pg_catalog.pg_database

select * from information_schema.views

select * from pg_catalog.pg_views;

SELECT
	*
FROM
	information_schema.columns
WHERE
	table_name = 'employee'
ORDER BY
	ordinal_position;

select * from pg_catalog.pg_indexes;

select * from information_schema.routines where routine_type = 'FUNCTION';

select * from information_schema.triggers;

SELECT nspname || '.' || relname AS "relation",
 pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
 FROM pg_class C
 LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
 WHERE nspname NOT IN ('pg_catalog', 'information_schema')
 AND C.relkind <> 'i'
 AND nspname !~ '^pg_toast'
 ORDER BY pg_total_relation_size(C.oid) DESC
 LIMIT 5;

SELECT
	pg_database.datname AS "database_name",
	pg_size_pretty(pg_database_size (pg_database.datname)) AS size_in_mb
FROM
	pg_database
ORDER BY
	size_in_mb DESC;

SELECT schemaname,relname,n_live_tup 
FROM pg_stat_user_tables 
ORDER BY n_live_tup DESC
LIMIT 12;

SELECT table_name, table_rows
FROM information_schema.tables
WHERE table_schema = (SELECT database())
ORDER BY table_rows DESC
LIMIT 12;