ORA-01791: 不是 SELECTed 表达式错误

SELECT DISTINCT
su.*, s. NAME post_name,
U .unit_code,
U .unit_name,
U .unit_id,
o.parent_id,
o.ORG_ORDER
FROM
v_sys_user su
LEFT JOIN sys_org o ON DECODE (
su.dept_id,
NULL,
su.org_id,
su.dept_id
) = o.org_id
LEFT JOIN sys_unit U ON o.org_no = U .unit_code
LEFT JOIN sys_code s ON o.org_no = s.code
WHERE
1 = 1
AND su.status = 1
ORDER BY
                                      su.user_id,
U .unit_id,
o.org_id,
o.org_order

DESC

错误原因：distinct后跟着的列名与order by 中对应的列名不一样，所以讲o.org_id改为o.parent_id就可以了