postgresql获取表结构，表名、表注释、字段名、字段类型及长度和字段注释

1、查询表名和表注释
select relname as tabname,
cast(obj_description(relfilenode,'pg_class') as varchar) as comment from pg_class c 
where   relname ='table_name' ;


2、查询字段名、字段类型及字段长度和字段注释
select a.attnum,a.attname,concat_ws('',t.typname,SUBSTRING(format_type(a.atttypid,a.atttypmod) from '\(.*\)')) as type,d.description from pg_class c, pg_attribute a , pg_type t, pg_description d 

where  c.relname = 'table_name' and a.attnum>0 and a.attrelid = c.oid and a.atttypid = t.oid and  d.objoid=a.attrelid and d.objsubid=a.attnum

注：table_name为表名