sql - 查询获取相交

Question

我正在解决一些有关SPJ数据库的问题。

S(SNUM, SNAME) [supplier]
P(PNUM, PNAME) [part]
J(JNUM, JNAME) [project]
SPJ(SNUM, PNUM, JNUM, Q)

查询是:获取至少有 100 个共同部分的项目对。
到目前为止我已经为其编写了代码:

SELECT X.JNUM, Y.JNUM FROM SPJ AS X, SPJ AS Y
    WHERE 100 <= (SELECT COUNT(PNUM) FROM (SELECT PNUM FROM SPJ WHERE SPJ.JN=X.JN 
                                            INTERSECT
                                           SELECT PNUM FROM SPJ WHERE SPJ.JN=Y.JN));

我认为我的解决方案是正确的。还有其他方法可以解决这个问题吗？

Answer 1

只需获取所有相同部分的组合，然后查看每个项目对获得多少匹配:

select spj1.jnum as jnum1, spj2.jnum as jnum2 
from spj spj1
join spj spj2 on spj1.pnum = spj2.pnum and spj1.jnum < spj2.jnum
group by spj1.jnum, spj2.jnum
having count(distinct spj1.pnum) >= 100;