查询表信息（表名/表描述）
select a.relname as name , b.description as value from pg_class a
left join (select * from pg_description where objsubid =0 ) b on a.oid = b.objoid
where a.relname in (select tablename from pg_tables where schemaname = 'public')
order by a.relname asc
查询列信息（列ID/列名/数据类型/长度/精度/是否可以为null/默认值/是否自增/是否是主键/列描述）
select ordinal_position as Colorder,column_name as ColumnName,data_type as TypeName,
coalesce(character_maximum_length,numeric_precision,-1) as Length,numeric_scale as Scale,
case is_nullable when 'NO' then 0 else 1 end as CanNull,column_default as DefaultVal,
case when position('nextval' in column_default)>0 then 1 else 0 end as IsIdentity,
case when b.pk_name is null then 0 else 1 end as IsPK,c.DeText
from information_schema.columns
left join (
select pg_attr.attname as colname,pg_constraint.conname as pk_name from pg_constraint
inner join pg_class on pg_constraint.conrelid = pg_class.oid
inner join pg_attribute pg_attr on pg_attr.attrelid = pg_class.oid and pg_attr.attnum = pg_constraint.conkey[1]
inner join pg_type on pg_type.oid = pg_attr.atttypid
where pg_class.relname = '表名' and pg_constraint.contype='p'
) b on b.colname = information_schema.columns.column_name
left join (
select attname,description as DeText from pg_class
left join pg_attribute pg_attr on pg_attr.attrelid= pg_class.oid
left join pg_description pg_desc on pg_desc.objoid = pg_attr.attrelid and pg_desc.objsubid=pg_attr.attnum
where pg_attr.attnum>0 and pg_attr.attrelid=pg_class.oid and pg_class.relname='表名'
)c on c.attname = information_schema.columns.column_name
where table_schema='public' and table_name='表名' order by ordinal_position asc
