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I was going through this link to see how the effective resultset looks like if we join (Inner/Outer) two tables.

I was just curious to know how the resultset looks like, If we perform Inner/Outer join on more than two tables?

Let's say I've three tables:

 1. USERS
 2. ADDRESS (Store User's address contains Foreign Key USERS.USER_ID)
 3. ITEMS (Contains Items that user sold contains foreign key USERS.USER_ID)

Now If I write a SQL:

SELECT ... FROM USERS users INNER JOIN ADDRESS address ON users.USER_ID = address.USER_ID
                            INNER JOIN ITEMS items ON users.USER_ID = items.USER_ID WHERE....

How the effective resultset will look like? Whether the DB creates two separate resultset pertaining to each JOIN condition or there will be a single resultset combining all the JOINS? When I say ResultSet, i mean how the effective DB structure looks like (as in the link I've mentioned on top).

Vicky
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1 Answers1

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Lets me Tell you brief description of the Inner Join And Outer Join. Simply join is for to view columns from two or more tables together.

Inner Join :- The Matched rows Of the Two or more Tables

SELECT ... FROM USERS users INNER JOIN ADDRESS address ON users.USER_ID = address.USER_ID INNER JOIN ITEMS items ON users.USER_ID = items.USER_ID WHERE....

What this Statement says is "SELECT ... FROM USERS users INNER JOIN ADDRESS address ON users.USER_ID = address.USER_ID" gives some rows with the filter specified.

INNER JOIN ITEMS items ON users.USER_ID = items.USER_ID WHERE.... :- statement adds columns of the table [ITEMS] with the specified criteria "users.USER_ID = items.USER_ID"

Outer Join :- Different Row of the table mean no rows matched in table.

Two type of the Outer Join Right Outer :- Not Matched row of the right side table Left Outer :-Not Matched row of the right side table

Sanjay
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