[英]PostgreSQL: update with left outer self join ignored
我想用TRUE
更新列leaf_category
,其中類別不是父類別。 它作為一個選擇語句:
select
c1.id, c1.name, c1.slug, c1.level, c2.parent_id, c2.name, c2.slug, c2.level
from
catalog_category c1
left outer join
catalog_category c2 on
(c1.id = c2.parent_id)
where
c2.parent_id is null;
但是,相應的UPDATE
將所有列設置為TRUE
。
update catalog_category
set leaf_category = True
from
catalog_category c1
left outer join
catalog_category c2 on
(c1.id = c2.parent_id)
where
c2.parent_id is null;
像這樣的UPDATE
可能嗎?
您只是缺少一個連接WHERE
子句:
UPDATE catalog_category c
SET leaf_category = true
FROM catalog_category c1
LEFT JOIN catalog_category c2 ON c1.id = c2.parent_id
WHERE c.id = c1.id
AND c2.parent_id IS NULL;
帶有NOT EXISTS
這種形式可能更快,執行相同的操作:
UPDATE catalog_category c
SET leaf_category = true
WHERE NOT EXISTS (
SELECT FROM catalog_category c1
WHERE c1.parent_id = c.id
);
有關的:
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