如何高效地反转多对多SQL查询？

Question

我有许多一对多的关系，我在其中查询具有特定的N-所有男，例如：

SELECT M.* FROM M INNER JOIN ManyToManyTable 
ON M.Id = ManyToManyTable.M 
WHERE ManyToManyTable.N = @Id 

或者：

SELECT M.* FROM M INNER JOIN ManyToManyTable 
ON M.Id = ManyToManyTable.M 
INNER JOIN N 
ON N.Id = ManyToManyTable.N 
WHERE N.Id = @Id 

我的问题是，如何以有效地反向查询，所以我得到所有M其中没有特定的N？

也就是说，像上面的选择NOT IN，但如果可能的话没有NOT IN声明。

Answer 1

在SQL Server 'NOT EXISTS' 一般more efficient比OUTER JOIN方法。

SELECT M.* FROM M 
WHERE NOT EXISTS 
(SELECT * FROM ManyToManyTable MMT 
      WHERE MMT.M = M.Id AND N=@Id) 

Answer 2

快速和肮脏的：

SELECT M.* FROM M 
WHERE M.id NOT IN 
    (SELECT M.id FROM M INNER JOIN ManyToManyTable 
    ON M.Id = ManyToManyTable.M 
    WHERE ManyToManyTable.N = @Id) 

更好：

SELECT M.* 
FROM M LEFT JOIN ManyToManyTable 
ON M.Id = ManyToManyTable.M 
WHERE ManyToManyTable.M IS NULL