Workaround for outer join with an IN operator in Oracle

问题

I am using Oracle SQL, so outer joins have the nice (+) syntax. I should warn you that I am not allowed to redesign the database; I work for a large organization.

Here are some example tables:

People
PersonID   Name
1          Elmo
2          Oscar
3          Chris

Attribute
PersonID   Attribute
1          Happy
1          Muppet
1          Popular
2          Grouchy
2          Muppet
2          Popular
3          Programmer

I want a list of people and I want to know whether we have knowledge of them being happy or grouchy. The following is the output I want:

Name       Mood
Elmo       Happy
Oscar      Grouchy
Chris

So here is the query I thought I would use:

SELECT p.Name, a.Attribute
FROM People p, Attributes a
WHERE p.PersonID = a.PersonID (+)
AND ( a.Attribute (+) = 'Happy'
   OR a.Attribute (+) = 'Grouchy' )

(Perhaps I would have to put "OR a.Attribute IS NULL" or something.)

But in fact I'm not allowed to use OR inside an outer join at all! What should I actually do instead?

回答1:

First of all, why can't you use proper OUTER JOINs?, you can use them in Oracle without having to do the implicit joins with the (+) syntax. As for your problem, you can use IN:

SELECT p.Name, a.Attribute
FROM People p
LEFT OUTER JOIN Attributes a
ON p.PersonID = a.PersonID AND a.Attribute IN ('Happy','Grouchy')

回答2:

If you really know the Oracel SQL syntax for a "proper" Oracle database, you could also do this...

SELECT p.Name,
       a.Attribute
  FROM people p,
       (SELECT PersonID,
               Attribute
          FROM attributes
              WHERE Attribute = 'Happy'
              OR Attribute = 'Grouchy') a
  WHERE p.personid = a.personid(+)

The point being that ANSI vs Oracle syntax is a ridiculous comment. Oracle supports both, you whichever is easier/better/manageable for you.

回答3:

Sorry to answer my own question. To avoid the error ORA-01719, I changed everything to "proper" joins at the advice of @Lamak, and then went with this solution:

SELECT p.Name, a.Attribute
FROM People p
LEFT OUTER JOIN  (SELECT PersonID, Attribute
                  FROM Attributes
                  WHERE Attribute = 'Happy' OR Attribute = 'Grouchy') a
ON (p.PersonID = a.PersonID)

来源：https://stackoverflow.com/questions/10758526/workaround-for-outer-join-with-an-in-operator-in-oracle

标签

sql

Oracle

outer-join