1、查询所有表名字，默认schema名字是public

SELECT
	tablename
FROM
	pg_tables
WHERE
	schemaname = 'public'

2、查询已知表名tableName的所有字段的字段名、类型、是否为空、注释

SELECT
	A.attname AS NAME,
	format_type(A.atttypid, A.atttypmod) AS TYPE,
	A.attnotnull AS NOTNULL,
	col_description(A.attrelid, A.attnum) AS COMMENT
FROM
	pg_class AS C,
	pg_attribute AS A 
WHERE
	C.relname = 'tableName' 
	AND A.attnum > 0
	AND A.attrelid = C.oid 

3、查询数据库相应用户userName的所有序列

SELECT
	* 
FROM
	pg_class 
WHERE
	relowner = (SELECT usesysid FROM pg_user WHERE usename = 'userName') 
	AND relkind = 'S'