直接查询系统表, 如:
mydb=# SELECT a.attnum,a.attname AS field,t.typname AS type,a.attlen AS length,a
.atttypmod AS lengthvar,a.attnotnull AS notnull
mydb-# FROM pg_class c,pg_attribute a,pg_type t
mydb-# WHERE c.relname = 'student' and a.attnum > 0 and a.attrelid = c.oid and a
.atttypid = t.oid
mydb-# ORDER BY a.attnum;