2

我有以下表格：
Person, {"Id", "Name", "LastName"}
Sports, {"Id" "Name", "Type"}
SportsPerPerson, {"Id", "PersonId", "SportsId"}

对于我的查询，我想获取所有从事特定运动的人，而我只有运动“名称”属性可供我使用。为了检索正确的行，我想出了以下查询：

SELECT *
FROM Person
WHERE Person.Id in 
(
    SELECT SportsPerPerson.PersonId FROM SportsPerPerson
    INNER JOIN Sports on SportsPerPerson.SportsId = Sports.Id
    WHERE Sports.Name = 'Tennis'
)
AND Person.Id in 
(
    SELECT SportsPerPerson.PersonId FROM SportsPerPerson
    INNER JOIN Sports on SportsPerPerson.SportsId = Sports.Id
    WHERE Sports.Name = 'Soccer'
)

或者

SELECT *
FROM Person
WHERE Id IN
    (SELECT PersonId FROM SportsPerPerson WHERE SportsId IN 
        (SELECT Id FROM Sports WHERE Name = 'Tennis'))
AND Id IN
    (SELECT PersonId FROM SportsPerPerson WHERE SportsId IN 
        (SELECT Id FROM Sports WHERE Name = 'Soccer'))

现在我的问题是，没有更简单的方法来编写这个查询吗？只使用 OR 是行不通的，因为我需要打“网球”和“足球”的人。但是使用 AND 也不起作用，因为这些值不在同一行上。

4

5 回答 5

2

You can use another JOIN to avoid the second IN. The sub-select only returns those persons that play both Tennis and Soccer:

SELECT *
FROM Person
WHERE Person.Id IN
(
    SELECT spp1.PersonId
    FROM SportsPerPerson spp1
    JOIN SportsPerPerson spp2 ON ( spp2.PersonId = spp1.PersonId )
    JOIN Sports s1 on spp1.SportsId = s1.Id
    JOIN Sports s2 on spp2.SportsId = s2.Id
    WHERE s1.Name = 'Tennis'
      AND s2.Name = 'Soccer'
)
于 2010-05-11T07:37:55.720 回答
1

You should use two joins in the query:

SELECT *
FROM Person p INNER JOIN SportsPerPerson spp1 ON (p.PersonId = spp1.PersonId)
              INNER JOIN Sports s1 ON (s1.SportsIN = spp1.SportId)
              INNER JOIN SportsPerPerson spp2 ON (p.PersonId = spp2.PersonId)
              INNER JOIN Sports s2 ON (s2.SportId = spp2.SportId)
    WHERE s1.Name = 'Tennis' AND s2.Name='Soccer'
于 2010-05-11T07:35:30.113 回答
0

您需要的查询是：

SELECT p.ID, p.Name, p.LastName
FROM Person p
JOIN SportsPerPerson sp ON p.ID = sp.PersonID 
JOIN Sports s ON sp.SportsID = s.ID
WHERE s.Name = 'Football'

也就是说，顺便说一句，SportsPerPerson 表上的 ID 键对于实现您拥有的多对多关系完全没有必要。使用 PersonID 和 SportID 列作为复合主键就足够了。

于 2010-05-11T07:51:31.920 回答
0

The trick is to use aliases so that you can use the same tables multiple times:

SELECT p.*
FROM Person p
INNER JOIN SportsPerPerson spa
  ON p.Id = spa.PersonId
INNER JOIN Sports sa
  ON spa.SportsId = sa.Id
INNER JOIN SportsPerPerson spb
  ON p.Id = spb.PersonId
INNER JOIN Sports sb
  ON spb.SportsId = sb.Id
WHERE
  sa.Name = 'Tennis'
  AND sb.Name = 'Soccer'
于 2010-05-11T07:39:04.040 回答
0

这个：

SELECT  *
FROM    Person p
WHERE   (
        SELECT  COUNT(*)
        FROM    Sports s
        JOIN    SportsPerPerson sp
        ON      sp.SportsID = s.id
        WHERE   s.name IN ('Tennis', 'Soccer')
                AND sp.PersonID = p.id
        ) = 2

或这个：

SELECT  p.*
FROM    (
        SELECT  sp.PersonID
        FROM    Sports s
        JOIN    SportsPerPerson sp
        ON      sp.SportsID = s.id
        WHERE   s.name IN ('Tennis', 'Soccer')
        GROUP BY
                sp.PersonID
        HAVING  COUNT(*) = 2
        ) q
JOIN    person p
ON      p.id = q.personID

您需要声明 aUNIQUE KEY或 a PRIMARY KEYonSportsPerPerson (sportsid, personid)才能正确快速地工作。

于 2010-05-11T07:41:10.527 回答