How to connect 4 tables?

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I need help as I just started learning SQL Server. I have this issue in appending the "required" columns from 4 different tables using SQL server and the problem here is that I want to connect the table even with a duplicate column name and display it all.

Database name is hower:

table 1: dep = dp, den

table 2: section = id, sec

table 4: users = id, fame, lame, deptID, section yearlevel

table 5: year= id, string

What I have tried:

I've tried doing right join, but I can only join two tables together with its column, but the data in each column had become null.

Posted 3-Apr-22 5:43am

Member 15356357

Updated 3-Apr-22 10:00am

Deeksha Shenoy

v4

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0x01AA 3-Apr-22 11:54am

Give this a try: Visual Representation of SQL Joins[^]

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OriginalGriff · Answer 1 · 2022-04-03T06:00:00

Solution 1

You can't join tables unless there is a relationship between them: they need to "share" information between them.

And there is nothing in your tables that is recognisably common data, except for a "deptID" in "table 4" which doesn't exist in any of the other three tables!

You JOIN tables when they do have a relationship: for example:
Invoices Table

ID
InvNumber
InvDate
CustID

InvoicceLines Table
ID

InvoiceID
Quantity
ProductID
PricePerUnit

Then to pick up the whole invoice, you use a JOIN:

SQL

SELECT i.InvNumber, il.*
FROM Invoices i
JOIN InvoiceLines il
  ON il.InvID = i.ID
WHERE i.InvNumber = 666

But if there is no relationship, there is nothing to JOIN!

Posted 3-Apr-22 6:00am

OriginalGriff

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Maciej Los 3-Apr-22 15:09pm

Short And To The Point!

Member 15356357 4-Apr-22 3:17am

is there any other way to connect them?

OriginalGriff 4-Apr-22 3:52am

Not unless there is some "common factor" - and we would have no idea what that was!

Think about it: how would you connect a list of pets and their names, ages, and preferred food with a list of cars that used a specific car park and their make, model, colour, and which parking space they used when?

You can't - because there is no common data, and nobody has any idea what a relationship might be. The two datasets may be related if the car park is exclusively used for pet store customers, but you and I have no idea if it is!

So think about your data and what it represents - identify what information relationships there are, and then you can start thinking about linking them.

Sorry, but we can't help you with that at all!