题
给定这两个表:
Foo (id, name) -- PK = id
Bar (fooId, value) -- PK = composite, fooId + value
-- value is a non-negative int
我怎样才能找到所有 Foo.name
s 没有对应的地方 Bar,value
高于 0?
例如:
Foo
id name
1 a
2 b
3 c
Bar
fooid value
1 0
1 1
2 0
3 4
Result:
b
解决方案
我发现以下内容最容易阅读和理解......
SELECT foo.name
FROM foo
WHERE NOT EXISTS (SELECT 'x'
FROM bar
WHERE bar.fooid = foo.id
AND bar.value > 0)
其他提示
SELECT Name
FROM Bar
INNER JOIN Foo ON Foo.Id = Bar.fooId
GROUP BY fooId, name
HAVING SUM(Value) = 0
该查询和 zodeus 发布的查询执行时间大约相同,但是该查询不会包含 Bar 表未引用的任何 Foo 记录。例如,如果您还有记录 Foo ( 4, d ),则此查询仍将返回“b”,而 zodeus 的查询将返回“b”和“d”。
SELECT name FROM FOO WHERE id NOT IN(
SELECT fooId FROM Bar GROUP BY fooId HAVING MAX(Value) > 0)
select Foo.name
from Foo
where Foo.id not in
(select Bar.fooid from Bar
where value > 0)
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