(My question has been asked a lot of times with two tables involved, and has been answered here, here and here. But I can't figure out how to do the same with three tables involved.)
I have three tables, A, B and C, where A has many B and B has many C. I want to join these tables and select zero or one rows per A, which one should be based on a condition in C.
Example, assume that:
SELECT
a.aId
,b.bId
,c.cId
FROM
a
INNER JOIN b ON b.aId=a.aId
INNER JOIN c ON c.bId=b.bId
WHERE
c.someColumn='foo'
...yields the following result:
aId bId cId
=== === ===
1 11 101
1 12 102
1 12 103
2 21 201
2 21 203
2 22 202
...then I would like to, for instance, retrieve two distinct A-rows, the ones with highest cId.
aId bId cId
=== === ===
1 12 103
2 21 203
You can use ROW_NUMBER:
WITH Cte AS (
SELECT
a.aId,
b.bId,
c.cId,
rn = ROW_NUMBER() OVER (PARTITION BY a.aId ORDER BY c.cId DESC)
FROM a
INNER JOIN b
ON b.aId = a.aId
INNER JOIN c
ON c.bId = b.bId
WHERE c.someColumn = 'foo'
)
SELECT
aId, bId, cId
FROM Cte
WHERE rn = 1
Related
I am inserting data to an already existing TableA and the following query is a part of a stored procedure. This part of the query inserts values into some columns of TableA. The stored procedure is very lengthy which has several insert statements to fill out the different columns in TableA.
INSERT INTO TableA (ID, Event, Date, Amount, Status_, Country)
(SELECT DISTINCT ID, Event, Date, Amount, c.Status, b.Country
FROM TableA1 a
JOIN TableB1 b ON b.employeeID = a.ID
JOIN TableC1 c ON c.Status = ‘Active’)
Usually, a join condition consists of two columns, for example (a.Status_ = c.Status). But here, it's replaced with a filter condition (JOIN TableC1 c ON c.Status = ‘Active’).
The select query alone executes well and returns results. I'm trying to understand the effect made by this filter condition.
Can you explain, please?
Thanks
It's the same as this...
SELECT DISTINCT
ID, Event, Date, Amount, c.Status, b.Country
FROM
(
TableA1 a
INNER JOIN
TableB1 b
ON b.employeeID = a.ID
)
CROSS JOIN
(
SELECT * FROM TableC1 WHERE Status = 'Active'
)
c
In effect, the INNER JOIN is resolved, and then each row from that is joined to every row from TableC1 WHERE Status = 'Active'
For example
TableA1
ID
Event
Date
Amount
1
e1
2022-01-01
11
2
e2
2022-02-02
22
TableB1
EmployeeID
Country
1
c1
2
c2
TableC1
some_id
Status
1
Sleeping
2
Active
3
Active
4
Sleeping
Would yield...
ID
Event
Date
Amount
Country
Status
(some_id, added by me)
1
e1
2022-01-01
11
c1
Active
2
1
e1
2022-01-01
11
c1
Active
3
2
e2
2022-02-02
22
c2
Active
2
2
e2
2022-02-02
22
c2
Active
3
You probably should have...
INNER JOIN
TableC1 c
ON c.some_id = b.some_other_id
AND c.Status = 'Active'
I have two tables (Books, Authors) with ManyToMany relationship. I need SQL statement to retrieve books with authors, sorted by authors/books. Important thing is that I must retrieve them with pagination (offset ... fetch in sql).
One of the problem that when I join tables there are duplicates in results (of course) and offset/fetch can't be used for this results. Another problem the results must be sorted (not subpages but all books of course).
I have one idea: (it retrieves books sorted by author name and include pagination)
select b.id, b.title, a.name from Books b inner join Books_Authors ba
on ba.bookID = b.id inner join Authors a
on ba.authorID = a.id
where a.name in (select name from Authors order by name offset 9 rows fetch next 3 rows only)
order by a.name
But I think it's not efficient way.
Something like this?
select * from
(
select tmp1.*, ROW_NUMBER() over(partition by b.title, a.name order by b.id, a.id) rang2
from
(
select a.id, b.id, b.title, a.name, ROW_NUMBER() over(partition by b.title, a.name order by b.id, a.id) rang
from Books b inner join Books_Authors ba on ba.bookID = b.id
inner join Authors a on ba.authorID = a.id
) tmp1 where rang=1
) tmp2
where rang2 between 3 and 9
order by title, name
table1
sno exam questions time_duration
1 unit test 1 10
2 mock 1 2 10
3 mock2 5 10
4 mock3 6 6
table2
qid answer user_attempt_option
1 1 1
2 2 3
2 3 4
3 4 1
3 1 2
3 2 3
3 3 1
I have two tables with schema and data as below. Table A has an id and an associated name. Table B associates the id from Table A with a price and otherAttr. For each entry in Table A, there may be multiple entries with different prices in Table B, but otherAttr is the same for each entry.
Given an id for Table A, I would like to select the name, otherAttr, and the minimum price.
The below query returns multiple results, I need to write a query that will return a single result with the minimum price.
SELECT a.name, b.price, b.otherAttr
FROM A a
LEFT Join B b on b.idFromA = 1
WHERE a.id = 1
Table A Table B
id | name idFromA | price | otherAttr
-------- ---------------------------
1 | A 1 | 200 | abc
2 | B 1 | 300 | abc
1 | 400 | abc
2 | 20 | def
2 | 30 | def
2 | 40 | ef
I massively oversimplified my example. In addition to selecting the min price and otherAttr from Table B, I also have to select a bunch of other attributes from joins on other tables. Which is why I was thinking the Group By and Min should be a subquery of the join on Table B, as a way to avoid Grouping By all the attributes I am selecting (because the attributes being selected for vary programmatically).
The Actual query looks more like:
SELECT a.name, b.price, b.otherAttr, c.x, c.y, d.e, d.f, g.h....
FROM A a
LEFT Join B b on b.idFromA = 1
LEFT Join C c on something...
LEFT Join D d on something...
LEFT Join G g on something...
WHERE a.id = 1
To get this, you could use GROUP BY in an INNER query:
SELECT gd.name, gd.price,gd.otherAttr, c.x, c.y, d.e, d.f, g.h....
FROM
(SELECT a.id,a.name, MIN(b.price) as price, b.otherAttr
FROM A a
LEFT Join B b on b.idFromA = 1
WHERE a.id = 1
GROUP BY a.id,a.name,b.otherAttr) gd
LEFT Join B b on b.idFromA = 1
LEFT Join C c on something...
LEFT Join D d on something...
LEFT Join G g on something...
Try:-
SELECT a.name, MIN(b.price) minprice, b.otherAttr
FROM A a
LEFT Join B b ON a.Id = b.idFromA
GROUP BY a.name, b.otherAttr
HAVING a.id = 1
You could just do this instead:
SELECT a.name, MIN(b.price), MIN(b.otherAttr)
FROM TableA a
LEFT JOIN TableB b on b.idFromA = a.id
GROUP BY a.name
HAVING a.id = 1;
You need to inner join on price as well in addition to id on the subquery to intersect the right record(s) with the lowest price(s). Then TOP(1) will return only one of those records. You can avoid using TOP(1) if you can expand the conditions and group by fields in the subquery so you schema can assure only a single record is returned for that combination of attributes. Lastly, avoid left joins when intersecting sets.
SELECT TOP(1) p.id, p.price, b.OtherAttr
FROM B as b
INNER JOIN
(SELECT A.id, min(B.price) as price
FROM B
INNER JOIN A on A.id=B.idFromA and A.ID=1
GROUP BY A.id) as p on b.idFromA=p.id and b.price=p.price
I have two Tables
Let suppose A and B
Now suppose the structure of table A is Like that
id stock
37 1
40 1
37 1
40 1
37 1
37 1
And B is like that
id stock
37 1
37 1
40 1
Now i want to write a query that give me sum of specific id stock in (table A - Table B) and if that id does not exist in table B then only stock from A.
So i will expect result like that
id stock
40 1
37 2
I thought that left join will be possible option here and i write query like that
SELECT A.id,
SUM(CAST(isNull(A.Stock, 0) as int) - CAST(isNull(B.Stock, 0) as int) )'Stock'
from A
LEFT OUTER JOIN
B
ON A.id = B.id
group by A.id
But Problem is that the above query gives desired records but wrong quantity/Stocklevel as shown below:
id stock
37 0
40 1
How can I resolve Stock Level issue.
I guess you are looking for something like this.
select A.id, A.SumA - coalesce(B.SumB, 0) as stock
from (
select A.id, sum(A.stock) as SumA
from A
group by A.id
) as A
left outer join
(
select B.id, sum(B.stock) as SumB
from B
group by B.id
) as B
on A.id = B.id
Result:
id stock
----------- -----------
37 2
40 1
SE Data
SELECT A.id, A.Stock - isNull(B.stock, 0) as Stock from A
LEFT OUTER JOIN B
ON A.id = B.id
That would be it I think.
PS. you group by something that you did not include in your case scenario. Your expected result is also not understandable to me (it conflicts with your problem description)
i have 3 tables (A,B,C)
Table A -
ID Name
1 Sam
2 Manuel
3 Jane
Table B
ID Tab_A_ID Name
1 1 Meer
2 1 Kutti
3 2 Mikaro
Table C
ID Tab_B_ID Price
1 1 255.11
2 1 30.52
3 3 125.22
I need a query that shall pick up the top price for TableA-Name from TableC. So only 1 top price for 1 nae record.
e.g.-
Sam - 255.11
Manuel - 125.22
How can i get this?
To get the max price per entry in A:
SELECT a.Name,
MAX(c.price)
FROM a
INNER JOIN b
ON a.id = b.tab_a_id
INNER JOIN c
ON b.id = c.tab_b_id
GROUP BY a.id, a.name
To get the max price per entry A per entry B:
SELECT a.Name,
b.Name
MAX(c.price)
FROM a
INNER JOIN b
ON a.id = b.tab_a_id
INNER JOIN c
ON b.id = c.tab_b_id
GROUP BY a.id, b.id, a.name, b.name
Note that entries in A without corresponding entires in B or entries in B without corresponding entries in C will not appear in the result. Use LEFT JOIN if you want to include these in the result.