sql 字符串长度 和 字符串后三位的取法

SELECT *
  FROM DIC_ITEM
WHERE DIC_CODE = 'FS990001'
   AND NOT EXISTS  (select * from organization_area o where o.area_code = item_code)
   AND PARENT_CODE = '320581405000'
   AND length(item_code) = 12
   AND substr(item_code, -3, 3) <> '000'
ORDER BY ITEM_CODE