Let's say I have the following table relationships (via keys existing on both ends)
table a -> table b
table b -> table c
table c -> table d
table d -> table e
table e -> table f
And I want to group by a key on table a and sum() values from table f as if both tables were directly joined.
Problem is that if I do that, information will be duplicated as all relationships from a -> b -> c -> d -> e -> f will repeat (as Andomar said: some information repeats because there are multiple routes from A to F)
Is there a way around that, or is my only choice to create a middle table containing the table a -> table f relationship?
Details:
Table a
id1 | id2
Table b
id2 | id3
Table c
id3 | value
select a.id1, sum(value) from a
inner join b on a.id2 = b.id2
inner join c on b.id3 = c.id3
group by a.id1
Data example:
Doing the join, the relationship is:
a b c value
1 2 2 20
1 3 2 20
1 4 2 20
If I do the sum(), I will get 60 but I want to get 20
Thanks
I'm assuming that some information repeats because there are multiple routes from A to F. If there is a unique key in F, you can un-duplicate the routes using a subquery:
SELECT SubQuery.AValue, sum(SubQuery.FValue)
FROM (
SELECT a.value as AValue, f.key, f.value as FValue
FROM a
INNER JOIN b ON b.key = a.key
INNER JOIN c ON c.key = b.key
INNER JOIN d ON d.key = c.key
INNER JOIN e ON e.key = d.key
INNER JOIN f ON f.key = e.key
GROUP BY a.value, f.key, f.value
) as SubQuery
GROUP BY SubQuery.AValue
The subquery ensures each row in F is only counted once.
Related
I have two tables:
Table A:
id names
1 a
2 b
3 c
and Table B:
id names
1 x
2 y
I'd like to perform a left join of Table B on Table A that results in the following table:
id names
1 x
2 y
3 c
How can I do this in Microsoft SQL?
You could use COALESCE:
SELECT a.id, COALESCE(b.name, a.name) AS name
FROM tab1 a
LEFT JOIN tab2 b
ON a.id = b.id
I think you just want coalesce():
select a.id, coalesce(b.name, a.name) as name
from a left join
b
on a.id = b.id;
Not sure if I can explain this well in words..
I want to find all items in Table B that have ALL items inactive for each item in Table A. Let's say Table A just has column "item" and Table B has columns "item" and "active"
Table A Table B
A A | 1
A A | 1
A B | 1
B B | 0
B C | 0
B C | 0
C D | 0
C E | 1
D
E
F
In that example, it should return C and D.
I managed to join tables A and B together with a group by clause but not sure where to go from there. Tried looking around and only found answers where the other table's value doesn't exist so you can use "NOT IN" but that doesn't seem to work here.
Any help would be appreciated!
You can join the tables and use the HAVING clause to make the comparison like this:
SELECT ta.Item
FROM TableA tA
LEFT JOIN TableB tB
ON tA.Item=tB.Item
GROUP BY tA.Item
HAVING SUM(tB.Inactive)=COUNT(tb.Inactive)
This would give you a distinct list of Items in TableA
The above query assumes 1 is Inactive and 0 is Active. If your data is opposite (which it looks like it is), you could instead say:
SELECT ta.Item
FROM TableA tA
LEFT JOIN TableB tB
ON tA.Item=tB.Item
GROUP BY tA.Item
HAVING SUM(tB.Inactive)=0
This would also return Item F as it doesn't have a value in table b to SUM. Just flip the LEFT JOIN to an INNER JOIN if you don't want Item F to return.
If you need to return back all instances in TableA, you could use a subquery and join to that:
SELECT ta.Item
FROM TableA tA
LEFT JOIN (SELECT ITEM, SUM(ACTIVE) Sum0 FROM TableB GROUP BY ITEM)tB
ON tA.Item=tB.Item
WHERE tB.Sum0 = 0
/*or tB.Sum0 is null would give you Item F*/
Use NOT EXISTS:
select distinct a.item
from table_A a
where not exists (select 1 from table_B b where b.item = a.item and b.status = 1);
I believe you would just need to join the tables together on table name and filter to only value of 0 on the active column.
SELECT B.*
FROM TableA A INNER JOIN TableB B ON A.item = B.item
WHERE B.active = 0
Does that get you what you need?
Ok so I will try to simplify the problem that I have.
I have 4 tables:
TableA:
OneID
TableB:
OneID (FK to TableA)
TwoID (FK to TableC)
TableC:
TwoID
ThreeID (FK to TableD)
TableD:
ThreeID
I need a query to retrieve data from all 4 of these tables.
The query criteria is:
want to inner join tables A, B, C
want to join above result with table D with the following conditions:
if a record is in Table D but not in Table C, then it must always be present in the results
otherwise if a record is in Table D and Table C, then it should only be present if it is in the result of the A,B,C join
The scenario you have described is not really possible (or at least they are not really logical)
if a record is in Table D but not in Table C, then it must always be present in the results
The only way a record could be "in Table D and not in Table C" is if the foreign key is null in table D, with no link from table D to tables A or B there is no other way you could define a record as being present in D and not in C:
otherwise if a record is in Table D and Table C, then it should only be present if it is in the result of the A,B,C join
Again, the only way this could happen is with NULLABLE foreign keys. Regardless I think any of the below will get you the results you require:
SELECT A.OneID, B.TwoID, c.ThreeID, D.FourID
FROM D
LEFT JOIN (C
INNER JOIN B
ON B.TwoID = C.TwoID
INNER JOIN A
ON A.OneID = B.OneID)
ON C.ThreeID = D.ThreeID;
Or
SELECT A.OneID, B.TwoID, c.ThreeID, D.FourID
FROM A
INNER JOIN B
ON B.OneID = A.OneID
INNER JOIN C
ON C.TwoID = B.TwoID
RIGHT JOIN D
ON D.ThreeID = C.ThreeID
Or
SELECT A.OneID, B.TwoID, c.ThreeID, D.FourID
FROM A
INNER JOIN B
ON B.OneID = A.OneID
INNER JOIN C
ON C.TwoID = B.TwoID
INNER JOIN D
ON D.ThreeID = C.ThreeID
UNION ALL
SELECT NULL, NULL, NULL, FourID
FROM D
WHERE ThreeID IS NULL;
Examples on SQL Fiddle
The first two have the same execution plan, it is just a matter of preference, I personally dislike using RIGHT JOIN because it makes queries feel like they in the wrong order i.e bottom to top, but this is purely my preference. The last query may perform better depending on the cardinality of your data and any indexes you have
EDIT
With your revised criteria I think the easiest way to implement this is with a UNION ALL:
SELECT A.OneID, B.TwoID, c.ThreeID, d3 = D.ThreeID
FROM A
INNER JOIN B
ON B.OneID = A.OneID
INNER JOIN C
ON C.TwoID = B.TwoID
INNER JOIN D
ON D.ThreeID = C.ThreeID
UNION ALL
SELECT NULL, NULL, NULL, ThreeID
FROM D
WHERE NOT EXISTS (SELECT 1 FROM C WHERE C.ThreeID = D.ThreeID);
Example on SQL Fiddle
I am not 100% sure I understood you correctly but I will try to help anyway. It seems that you need to do FULL OUTER JOIN on table D:
SELECT
*
FROM
TableA AS A INNER JOIN
TableB AS B ON B.A_Id = A.Id INNER JOIN
TableC AS C ON C.B_Id = B.Id FULL OUTER JOIN
TableD AS D ON D.C_Id = C.Id
If I have misunderstood your requirements and you need more complicated criteria, you could just do FULL OUTER JOIN on all the tables and put extra conditions in WHERE part:
SELECT
*
FROM
TableA AS A FULL OUTER JOIN
TableB AS B ON B.A_Id = A.Id FULL OUTER JOIN
TableC AS C ON C.B_Id = B.Id FULL OUTER JOIN
TableD AS D ON D.C_Id = C.Id
WHERE
--if a record is in Table D but not in Table C, then it must always be present in the results
(D.Id IS NOT NULL AND C.Id IS NULL) OR
(
--otherwise if a record is in Table D and Table C, then it should only be present if it is in the result of the A,B,C join
(D.Id IS NOT NULL AND C.Id IS NOT NULL) AND
--want to inner join tables A, B, C
(A.Id IS NOT NULL AND B.Id IS NOT NULL AND B.Id IS NOT NULL)
)
I have three tables A, B, and C:
A
---------
a_pk | id
B
----------------------
b_pk | id | link | foo
C
----------------------
c_pk | id | link | bar
All records in B have a matching record in A; all records in C have a matching record in A, but records in B and C do not necessarily have to match each other. I want to get the set of results where A has a match in either B or C. Individually, the queries would be:
SELECT A.id, B.foo FROM A INNER JOIN B ON A.id = B.id
SELECT A.id, C.bar FROM A INNER JOIN C ON A.id = C.id
SELECT B.foo, C.bar FROM B FULL JOIN C ON B.id = C.id AND B.link = C.link
What would I need to fill in to make this work?
SELECT A.id, B.foo, C.bar FROM <join A, B, C>
I'm using Oracle if it makes a difference, and I would prefer to avoid using a subquery if possible.
[edit - for clarification]
I want only the records from A that have a match in either B or C.
Sounds like you need a left join. (I'm not very familiar with Oracle but I assume this should work.)
SELECT A.id, B.foo, C.bar
FROM A
LEFT OUTER JOIN B on A.id = B.id
LEFT OUTER JOIN C on A.id = C.id
WHERE B.id IS NOT NULL OR C.id IS NOT NULL
I have a table A with columns (Id,Value)
and a table B with Columns (BId,Id,..)
and a table C with columns (CId,Id,...)
I need to perform an inner join on these tables as follows
select a.Id,a.Value from A a
inner join B b on b.Id=a.Id
inner join C c on c.Id=a.Id
where <many conditions on table B and C>
How can i achieve the same. Now when i just run the query
select a.Id,a.Value from A a
inner join B b on b.Id=a.Id
inner join C c on c.Id=a.Id
it doesnt return anything.. please help.
FYI when i run the joins separately it gives me the rows. I just want a union of them...
Sample data:
A
1
2
3
B
2
C
3
then i want to select
A
2
3
Thanks in advance.
So, following your comments, it appears that you want something like this:
select a.Id,a.Value from A a
inner join B b on b.Id=a.Id
where <many conditions on table B>
UNION ALL
SELECT a.Id, a.Value from A
inner join C c on c.Id=a.Id
where <many conditions on table C>
As long as the fields match on ID from A -> B and A -> C and you dont have any other join condition, you should be able to see the matching rows.
I could not understand your point about how the B and C Id do not match. if a.id=b.id and a.id=c.id, Doesn't it automatically imply b.id = c.id?
Anyways, in situations like these, I try to do outer join of A on B and C and see if the rows that I think are matching in fact do exist.
select a.Id,a.Value from A a
left outer join B b on b.Id=a.Id
left outer join C c on c.Id=a.Id
where (b.id is not null or c.id is not null)
/* Matching record found in b or c */
EDIT: Based on your requirement, you can use the approach that Lamak suggested above (Using UNION Alls) or if you are certain that for each record in A, you will only have one record in B and one in C at most and only one column, you can use the scalar sub query approach.