Converting From NOT EXISTS to NOT IN

问题

I have three tables:

• sailor (sname, rating);
• boat (bname, color, rating);
• reservation (sname, bname, weekday, start, finish);

In order to get a list of sailors who have reserved every red boat, I have:

select s.sname from sailor s 
where not exists(  
    select * from boat b  
    where b.color = 'red'  
    and not exists (  
        select * from reservation r  
        where r.bname = b.bname  
        and r.sname = s.sname));

I now need to rewrite this query with NOT IN instead of NOT EXISTS. Here's what I have so far:

select s.sname from sailor s
where s.sname not in (select s2.sname from sailor s2 where
    s2.sname not in (select r.sname from reservation r where r.bname not in (
            select b.bname from boat b where b.color <> 'red' )));

This, however, returns a list of all sailors who have reserved a red boat (not necessarily all of them). I'm having great difficulty checking whether or not a name in the list has reserved EVERY boat (I also cannot use COUNT()).

Any help is appreciated

回答1:

Inorder to get a list of sailors who have reserved every boat. I'll use this script

Solution 1:

 ;WITH k AS 
    (
    SELECT b.sname,COUNT(distinct a.bname) coun FROM boat a
    INNER JOIN reservation b 
        on a.bname = b.bname
    GROUP BY b.sname
    )
    SELECT k.sname FROM k WHERE coun = (select COUNT(*) FROM boat AS b)

Solution 2:

SELECT s.sname
FROM   sailor AS s
WHERE  s.sname NOT IN (SELECT DISTINCT a.sname
                       FROM   (SELECT s.sname,
                                      b.bname
                               FROM   sailor AS s
                                      CROSS JOIN boat AS b
                               WHERE  b.color = "Red") a
                       WHERE  a.sname + a.bname 
                                            NOT IN (SELECT r.sname + r.bname
                                                    FROM   reservation AS r
                                                    WHERE  r.sname IS NOT NULL
                                                            AND r.bname IS NOT NULL));

回答2:

This is funny; you can maintain the syntactic structure (correlated subqueries) while replacing NOT EXISTS ( ... ) by IN ( ...) :

SELECT s.sname from sailor s
WHERE 13 NOT IN (
    SELECT 13 FROM boat b
    WHERE b.color = 'red'
    AND 42 NOT IN (
        SELECT 42 from reservation r
        WHERE r.bname = b.bname
        AND r.sname = s.sname
       )
    );

来源：https://stackoverflow.com/questions/26697519/converting-from-not-exists-to-not-in