1、执行sql语句 

SELECT 
    A.attnum AS "序号",
    C.relname AS "表名",
    CAST ( obj_description ( relfilenode, 'pg_class' ) AS VARCHAR ) AS "表名描述",
    A.attname AS "字段名称",
    A.attnotnull as "是否不为null",
    (case when A.attnotnull = 't' then '是' else '否' end) as "是否必填",
    concat_ws ( '', T.typname, SUBSTRING ( format_type ( A.atttypid, A.atttypmod ) FROM '\(.*\)' ) ) AS "数据类型",
    T.typname as "字段属性",
    SUBSTRING(SUBSTRING ( format_type ( A.atttypid, A.atttypmod ) FROM '\(.*\)' ) from '\(([^)]+)\)') as "长度",
    d.description AS "备注"
FROM
    pg_class C,
    pg_attribute A,
    pg_type T,
    pg_description d 
WHERE
<--     C.relname = 'sys_user'    AND  -->
    A.attnum > 0 
    AND A.attrelid = C.oid 
    AND A.atttypid = T.oid 
    AND d.objoid = A.attrelid 
    AND d.objsubid = A.attnum 
ORDER BY
    C.relname DESC,
    A.attnum ASC

2、导出查询结果