我有以下的SQL语句:
select
DOCUMENT.DOCUMENT_ID,
(case
when DOCUMENT.CLASSIFICATION_CODE is not null
then DOCUMENT.CLASSIFICATION_CODE
else TEMPLATE.CLASSIFICATION_CODE end) CLASSIFICATION_CODE,
CLASSIFICATION.NAME CLASSIFICATION_NAME
from
DOCUMENT,
TEMPLATE,
CLASSIFICATION
where
DOCUMENT.TEMPLATE_ID = TEMPLATE.TEMPLATE_ID and
DOCUMENT.CLASSIFICATION_CODE = CLASSIFICATION.CLASSIFICATION_CODE(+)
What I would like to do is along the lines of:
if DOCUMENT.CLASSIFICATION_CODE IS NOT NULL THEN
DOCUMENT.CLASSIFICATION_CODE = CLASSIFICATION.CLASSIFICATION_CODE(+),
ELSE
TEMPLATE.CLASSIFICATION_CODE = CLASSIFICATION.CLASSIFICATION_CODE(+)
可以的吗?
JOIN
语法。谁能记得在WHERE
子句中(+)
的含义? - Gordon Linoff