如何从笛卡尔乘积查询中追加 table 中尚不存在的记录？

Question

我当前的查询 returns 来自 2 table 的所有可能结果，并将它们插入连接点 table。

我当前的查询如下所示：

INSERT INTO tblJunction_Courses_Software ( CourseID, SoftwareID )
SELECT tblCourses.CourseID, tblSoftware.SoftwareID
FROM tblSoftware, tblCourses
WHERE (((tblSoftware.Exclude)=No));

如何添加附加子句以确保每次查询时都不会附加重复数据运行？

Answer 1

我想你可以用 not exists 子句做你想做的事:

INSERT INTO tblJunction_Courses_Software ( CourseID, SoftwareID )
     SELECT c.CourseID, s.SoftwareID
     FROM tblSoftware as s CROSS JOIN tblCourses as c
     WHERE s.Exclude = No AND
           NOT EXISTS (SELECT 1
                       FROM tblJunction_Courses_Software as cs
                       WHERE cs.CourseId = c.CourseId AND
                             cs.SoftwareId = s.SOftwareId
                      );

如何从笛卡尔乘积查询中追加 table 中尚不存在的记录？

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