T-SQL 如何根据其他表中的列列出表中不存在的行

Question

Looking for some help in what is likely quite a simple problem but the wording makes it hard for me to see if a similar question has been asked.

In SQL Server I have 3 tables:

• Colleague (ColleagueID (INT), Name (NVARCHAR), Branch )
• Module (ModuleID (INT), Course (NVARCHAR), DueDate)
• ModuleCompletion (RecordID (INT), Colleague (NVARCHAR), Module (NVARCHAR)

This is a quickly constructed set of tables based on the data collected previously which the company stored in Excel, eg A Worksheet Matrix of (Colleagues Down Y) and (Modules Across X) and a 1 for completed and a 0 for not completed.

I grabbed all the 1's and uploaded them to a ModuleCompletion table to keep track of who completed what.
As it stands there are no Foreign Keys linking the tables and no UNIQUES etc.

Example tables:

Colleague

ID   Name  Branch  
-----------------
1    xyz    HO  
2    abc    HO  
3    tuv    HO  
4    efg    Branch1

Module

ID   Course  DueDate  
-----------------------
1    Co1     2019-12-31  
2    Co2     2020-01-30  

ModuleCompletion

ID   Colleague  Module
-----------------------
1    xyz        Co1
2    xyz        Co2
3    abc        Co1
4    tuv        Co2

What I am looking to have returned is:

Module  Branch   Colleague
--------------------------
Co1     HO       tuv
Co1     Branch1  efg
Co2     HO       abc
Co2     Branch1  efg

The result set should be each Branch and colleague combination not listed with a Module in the ModuleCompletion table.

Using:

SELECT c.Branch, c.Name
FROM Colleague c
LEFT JOIN ModuleCompletion x ON x.Colleague = c.Name 
WHERE x.Colleague IS NULL
ORDER BY c.Branch, c.Name

Displays all branch and colleague names where they have completed no courses, eg the Colleague name never appears in the ModuleCompletion table, but I need it to check by module.

Any help will be appreciated.

Answer 1

Don't left join, but cross join.

from Colleague c
cross join Module m
where not exists (
  select *
  from ModuleCompletion mc
  where c.Name   = mc.Colleague
  and   m.Course = mc.Module
)

Basically you can play on from here

Answer 2

Based on the previous solution and to avoid nested select you could do something like that too:

SELECT m.Course, c.Branch, c.Name 
  FROM Collegue     as c
 CROSS JOIN Module  as m
EXCEPT 
SELECT m.Course, c.Branch, c.Name
  FROM ModuleCompletion as mc
 INNER JOIN Collegue    as c 
         ON c.Name      = mc.Colleague
 INNER JOIN Module      as m
         ON m.Course    = mc.Module