连接的用法：获得相反的结果

Question

我正在使用oracle，下面我有一个基本的SQL查询，我选择了一个团队使用join的学校。然而，我正在努力如何使用连接选择相反的（没有团队的学校）。我尝试使用outter，inner，left和right这两个词，但无济于事，我得到了我想要的结果。如何列出没有团队的学校？

查询：

SELECT DISTINCT a.school_name, a.school_id, b.school_id FROM School a RIGHT OUTER JOIN Team b ON a.school_id = b.school_id;

结果：

SCHOOL_NAME               SCHOOL_ID  SCHOOL_ID
------------------------- ---------- ----------
Panthers University          92022      92022
Blue Rays Middle School      22149      22149

表：

schools

 SCHOOL_ID SCHOOL_NAME                   SCHOOL_TYPE
---------- ----------------------------- ------------
     92022 Panthers University           University
     22149 Blue Rays Middle School       Middle SchooL
     21719 Bull Dogs High School         High SchooL
     42736 Saint Lucia Grade School      Middle SchooL

school_teams

   TEAM_ID   SPORT_ID  SCHOOL_ID TEAM_NAME
---------- ---------- ---------- ----------
         1          1      92022  Panthers
         2          1      22149 Blue Rays

Answer 1

使用Not exists执行此操作。

SELECT a.school_name, a.school_id 
FROM School a 
where not exists (select 1 from Team b where a.school_id = b.school_id)

Answer 2

所有这些连接（内部，外部，左侧，右侧）仅选择匹配的行。您正在寻找不匹配的行，因此它们不适合您。

试试这个：

SELECT DISTINCT school_id, school_name FROM school 
  WHERE school_id not in
    (SELECT school_id FROM school_teams)

Answer 3

尝试：

SELECT DISTINCT a.school_name, a.school_id, b.school_id FROM School a LEFT OUTER JOIN Team b ON a.school_id = b.school_id;

Answer 4

编写此查询以生成所需的结果集。使用左加入。

SELECT Table1.School_Name, Table1.School_Id FROM Table1 LEFT JOIN Table2 ON Table1.School_Id = Table2.School_Id where  Table1.School_Id NOT IN (Select DISTINCT Table2.School_Id From Table2);