mysql - 协助 SQL 查询返回不匹配的单元格

Question

我有以下 2 个表:

表1

[schoolName] [Track] [Student Name] [Program ID]   
ABC          103     joe            1
ABC          101     Edward         2
QWE          103     Adam           5
QWE          103     Ben            1

表2

[SchoolName] [Program ID] [Class ID] [Class Name]
ABC          1            1          Science
ABC          1            2          Math
ABC          1            3          History
ABC          2            1          Science
QWE          5            1          Science
QWE          5            2          Math
QWE          1            2          Math

希望选择参加 track#103 programs not cover class#3 的学生姓名，并为他们的类(class)名称返回 NULL，如下结果:

[schoolName] [Track] [Student Name] [Program ID] [Class Name]
QWE          103     Adam           5            NULL
QWE          103     Ben            1            NULL

我正在尝试以下查询但它不起作用:

select Table1.[schoolName], Table1.[Track], Table1.[Student Name], Table1.[Program ID], Table2.[Class Name] 
from table1, table2 
where Table1.[schoolName]=Table2.[SchoolName] 
  and Table1.[Program ID]=Table2.[Program ID] 
  and Table1.[Track]=103
  and Table2.[Class ID] = 3 
   OR Table2.[Class ID] IS NULL

我做错了什么？

Answer 1

首先，我非常怀疑您使用的是 MySQL 还是 Oracle。引用 [] 是特定于 SQL Server 的。

Looking to select student names attending track# 103 programs not covering class# 3 and return NULL for their class name

您可以首先从 table1 中获取所有记录，其中 track 为 103，然后使用相关子查询来消除程序包含 class id = 3 的行:

SELECT T1.[schoolName],
       T1.[Track],
       T1.[Student Name],
       T1.[Program ID],
       NULL AS [Class Name] 
FROM table1 T1
WHERE T1.[Track] = 103
  AND NOT EXISTS (SELECT 1
                  FROM table2 T2
                  WHERE T1.[SchoolName] = T2.[SchoolName]
                    AND T1.[Program ID] = T2.[Program ID]
                    AND T2.[Class ID] = 3);

LiveDemo

考虑使用不带空格的列名，例如 Program_ID、Class_ID 等。