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SQL Left join, how to include empty rows

I have got the following 2 tables:

amounts
--------
userfk
transfk
amount

AND

users
-------
userid
name

I would like to have a query, that returns for a certain transfk ALL users with either the amount or a NULL value. For example: I have got 3 users, for transfk = 14 only 2 users have got an amount:

userid  name    amount  transfk
------  -------     ------      --------
1       Ronald         3       14
2       John            4       14
3       Austin        NULL    14

What query do I have to perform. To make it a bit clearer, the tables contain the following values:

amounts:
userfk   transfk   amount
-------  --------  --------
1        14        3
2        14        4
2        17        1

users:
userid   name
-------  ----------
1        Ronald
2        John
3        Austin

Any suggestions?
0
dutchdevelopment
Asked:
dutchdevelopment
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1 Solution
 
adatheladCommented:
Hi,

This should dot it:

SELECT userid, name, amount
FROM users
     LEFT JOIN amounts ON userid = userfk
WHERE transfk IS NULL or transfk = 14

Cheers
0
 
dutchdevelopmentAuthor Commented:
Unfortunately this won't work in all cases.

It'll work in this case because both users 1 and 2 have an entry for transfk = 14 and user 3 doesn't have an entry at all.

But when you do the same for transfk = 17 you will get no entry for user 1 (Ronald):

userid  name    amount  transfk
------  -------     ------      --------
2       John            1        17
3       Austin        NULL    17

Any clues?
0
 
koutnyCommented:
SELECT userid, name, amount
FROM users
     LEFT JOIN amounts ON (userid = userfk AND transfk = 14)
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dutchdevelopmentAuthor Commented:
Thanks all.

I have used the answer of koutny as a starter with the following added:

SELECT userid, name, amount
FROM users
LEFT JOIN amounts ON (users.userid = amounts.userfk AND amounts.transfk = 17 OR amounts.transfk IS NULL)
0
 
Julian HansenCommented:
This might do it (modify fields you need to see)

select * from users left join
(
SELECT userid, name, amount, transfk
FROM users
     LEFT JOIN amounts ON userid = userfk
WHERE transfk IS NULL or transfk = 14
) A on A.name = users.name

0
 
koutnyCommented:
Hi, I don't think that any addition or modificiation is needed.
It is the property of the LEFT OUTER JOIN that it will return ALL records from the table on the left side on the join (i.e. users) and it will fill in the remaining columns from the table on the right side of the join if the the ON (...) condition is true, otherwise it will fill those columns with null values.
0
 
Julian HansenCommented:
You are right - delayed post on my part. I opened this thread before your response and obviously replied after you. We have such slow lines here that tomorrow and next week mean the same thing ;)

Your post is much better - simplier.
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dutchdevelopmentAuthor Commented:
koutny:
It is necessary to add the modification (at least in MS Access 2000).
I think that the addition of amounts.transfk = 17 has undone the "return ALL records"-effect of a LEFT OUTER JOIN.
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