需要包括一些結果從不IN

Question

我有一個SQL小提琴在這裏http://sqlfiddle.com/#!2/c6222/1需要一點幫助。

我需要返回任何group_id，其中有一個user_id，該group_id在該group_id內沒有'GROUP'設置。我在SQL小提琴中的查詢正在刪除13565，因爲它在不同的group_id中具有「GROUP」。

這很簡單，但我無法得到它。

CREATE table role(
    role_id int, 
    role_type varchar(255), 
    group_id int, 
    user_id int 
); 

INSERT INTO role VALUES(71002,'Group',1465,8301); 
INSERT INTO role VALUES(71000,'Training_admin',1465,7959); 
INSERT INTO role VALUES(71003,'Training_admin',1465,8301); 
INSERT INTO role VALUES(71001,'Training_User',1465,7959); 
INSERT INTO role VALUES(71004,'Training_User',1465,8301); 
INSERT INTO role VALUES(71005,'Training_User',1465,13541); 
INSERT INTO role VALUES(493513,'Initial',6314,13565); 
INSERT INTO role VALUES(493522,'Ongoing',6314,13565); 
INSERT INTO role VALUES(493534,'Initial',3128,13565); 
INSERT INTO role VALUES(493556,'Group',3128,13565); 

select * from role 
where user_id not in (select role.user_id 
    from role 
    where role.role_type = 'GROUP') 

Answer 1

使用NOT EXISTS代替NOT IN，這允許多個謂詞：

SELECT * 
FROM Role AS r 
WHERE NOT EXISTS 
     ( SELECT 1 
      FROM role AS r2 
      WHERE r2.user_id = r.user_id 
      AND  r2.group_id = r.group_id 
      AND  r2.role_type = 'GROUP' 
     ); 

話雖這麼說，MySQL performs better using LEFT JOIN/IS NULL over NOT EXISTS，所以你應該爲改寫：

SELECT r.* 
FROM Role AS r 
     LEFT JOIN role AS r2 
      ON r2.user_id = r.user_id 
      AND r2.group_id = r.group_id 
      AND r2.role_type = 'GROUP' 
WHERE r2.role_id IS NULL; 

Answer 2

下面是該查詢你正在尋找沒有子查詢（爲了更好的性能）：

SELECT * 
FROM role R 
LEFT OUTER JOIN role R2 ON R2.user_id = R.user_id 
          AND R2.role_type = 'GROUP' 
WHERE R2.user_id IS NULL 

希望這會對你有所幫助。