I'm using Oracle (SQL*Plus) and I currently have the following tables:
USERS:
Id|Name|Gender
1 |A |M
2 |B |F
3 |C |M
4 |D |F
FRIENDS
Id1|ID2
1 |2
1 |3
2 |3
2 |4
2 |1
3 |1
3 |2
4 |2
How would I query,"For each user, find the number of male and female friends?"
I need an output that looks like this:
Id|Male Friends|Female Friends
1 |1 |1
2 |2 |1
3 |1 |1
4 |0 |1
I appreciate the help.
Make a query with two outer joins - one to male friends, and another one to female friends. Group by user ID:
SELECT u.Id, COUNT(m.Id) as MaleFriends, COUNT(f.Id) as FemaleFriends
FROM Users u
LEFT OUTER JOIN Friends ff ON u.Id=ff.Id1
LEFT OUTER JOIN Users m ON ff.Id2=m.Id AND m.Gender='M'
LEFT OUTER JOIN Users f ON ff.Id2=f.Id AND f.Gender='F'
GROUP BY u.Id
The reason the counts of m.Id and f.Id would be different is that when a row of FRIENDS joins to a male friend, f.Id would be NULL, and vice versa. COUNT skips NULL values, producing the counts that you need.
Related
Background
Forgive the title of this question, as I'm not really sure how to describe what I'm trying to do.
I have a SQL table, d, that looks like this:
+--+---+------------+------------+
|id|sex|event_type_1|event_type_2|
+--+---+------------+------------+
|a |m |1 |1 |
|b |f |0 |1 |
|c |f |1 |0 |
|d |m |0 |1 |
+--+---+------------+------------+
The Problem
I'm trying to write a query that yields the following summary of counts of event_type_1 and event_type_2 cut (grouped?) by sex:
+-------------+-----+-----+
| | m | f |
+-------------+-----+-----+
|event_type_1 | 1 | 1 |
+-------------+-----+-----+
|event_type_2 | 2 | 1 |
+-------------+-----+-----+
The thing is, this seems to involve some kind of transposition of the 2 event_type columns into rows of the query result that I'm not familiar with as a novice SQL user.
What I've tried
I've so far come up with the following query:
SELECT event_type_1, event_type_2, count(sex)
FROM d
group by event_type_1, event_type_2
But that only gives me this:
+------------+------------+-----+
|event_type_1|event_type_2|count|
+------------+------------+-----+
|1 |1 |1 |
|1 |0 |1 |
|0 |1 |2 |
+------------+------------+-----+
You can use a lateral join to unpivot the data. Then use conditional aggregate to calculate m and f:
select v.which,
count(*) filter (where d.sex = 'm') as m,
count(*) filter (where d.sex = 'f') as f
from d cross join lateral
(values (d.event_type_1, 'event_type_1'),
(d.event_type_2, 'event_type_2')
) v(val, which)
where v.val = 1
group by v.which;
Here is a db<>fiddle.
I have 3 tables:
Products
Groups
Sales
The products table contains the following information:
|**Product ID**|**Product Description**|
|--------------|-----------------------|
|1 |Wine |
|2 |Ruler |
|3 |Gas |
|4 |Water |
The Groups table contains the following information:
|**Group ID**|**Group Description**|
|------------|---------------------|
|1 |Cheetahs |
|2 |Elephants |
|3 |Cougars |
The Sales table contains the following information:
|**GroupID**|**Product ID**|**Amount Sold**|**Day Sold**|
|-----------|--------------|---------------|------------|
|1 |2 | 3|07-31-2016 |
|1 |1 | 1|07-31-2016 |
|2 |3 | 5|07-31-2016 |
|1 |4 | 2|08-01-2016 |
Now I have to produce a query that could bring me a result set as follows (with the condition that I want only results from 07-31-2016):
|**Group ID**|**Product ID**|**Amount Sold**|
|------------|--------------|---------------|
|1 |1 |1 |
|1 |2 |3 |
|1 |3 |0 |
|1 |4 |0 |
|2 |1 |0 |
|2 |2 |0 |
|2 |3 |5 |
|2 |4 |0 |
|3 |1 |0 |
|3 |2 |0 |
|3 |3 |0 |
|3 |4 |0 |
I thought this was going to be just a matter of using left joins, but it appears it wouldn't bring me back the result I was looking for (I don't want to omit products nor groups which weren't sold).
So in summary, I need to display all groups and all products no matter if they had an appearance in the Sales table.
I would appreciate any feedback on this matter, directions on where to look at or any logic that I may be missing!
EDIT
I've marked Matt's (big thanks) post as the answer, turns out I've never used a cross join.
I only added the where clause inside the left join of the Sales table in order to get just the sales made on 07-31-2016
SELECT
g.GroupId
,p.ProductId
,SUM(COALESCE(s.AmountSold,0)) as AmountSold
FROM
Products p
CROSS JOIN Groups g
LEFT JOIN Sales s
ON p.ProductId = s.ProductId
AND g.GroupId = s.GroupId
AND daySold = '07-31-2016'
GROUP BY
g.GroupId
,p.ProductId
ORDER BY
g.GroupId
,p.ProductId
SELECT
g.GroupId
,p.ProductId
,SUM(COALESCE(s.AmountSold,0)) as AmountSold
FROM
Products p
CROSS JOIN Groups g
LEFT JOIN Sales s
ON p.ProductId = s.ProductId
AND g.GroupId = s.GroupId
AND s.daySold = '07-31-2016'
GROUP BY
g.GroupId
,p.ProductId
ORDER BY
g.GroupId
,p.ProductId
Note your expected results you provided are wrong for group 1 product 4 there were 2 of those in the sale.
You could join all the Products with all the Groups (so you get a list of all the combinations of the two) and then add the additional information (filtering out the results based on your condition with a WHERE statement.
SELECT A.[Group ID]
, B.[Product ID]
, ISNULL([Amount Sold], 0) AS 'Amount Sold'
FROM Groups A
INNER JOIN Products B
ON 1 = 1
LEFT JOIN Sales C
ON C.[Group ID] = A.[Group ID]
AND C.[Product ID] = B.[Product ID]
WHERE [Day Sold] = '07-31-2016'
Let's say I have a table customers:
-----------------
|id|name|country|
|1 |Joe |Mexico |
|2 |Mary|USA |
|3 |Jim |France |
-----------------
And a table languages:
-------------
|id|language|
|1 |English |
|2 |Spanish |
|3 |French |
-------------
And a table cust_lang:
------------------
|id|custId|langId|
|1 |1 |1 |
|2 |1 |2 |
|3 |2 |1 |
|4 |3 |3 |
------------------
Given a list: ["English", "Spanish", "Portugese"]
Using a WHERE IN for the list, it will still return customers with ids 1,2 because they match "English" and "Spanish".
However, the results should be 0 rows returned since no customer matches ALL three terms.
I only want the customer ids to return if it matches the cust_lang table.
For instance, Given a list: ["English", "Spanish"]
I would want the results to be customer Id 1, since he alone speaks both languages.
EDIT: #GordonLinoff - That works!!
Now to make it more complex, what's wrong with this additional related query:
Let's assume I also have a table degrees:
-----------
|id|degree|
|1 |PHD |
|2 |BA |
|3 |MD |
-----------
A corresponding join table cust_deg:
------------------
|id|custId|degId |
|1 |1 |1 |
|2 |1 |2 |
|3 |2 |1 |
|4 |3 |3 |
------------------
The following query does not work. However, it is two of the same queries combined. The results should be only rows that match both lists, instead of the one list.
SELECT * FROM customers C
WHERE C.id IN (
SELECT CL.langId FROM cust_lang CL
JOIN languages L on CL.langId = L.id
WHERE L.language IN ("English", "Spanish")
GROUP BY CL.langID
HAVING COUNT(*) = 2)
AND C.id IN (
SELECT CD.custId FROM cust_deg CD
JOIN degrees D ON CD.degID = D.id
WHERE D.degree IN ("PHD", "BA")
GROUP BY CD.custId HAVING COUNT(*) = 2));`
EDIT2: I think i fixed it. I accidentally had an extra select statement in there.
You can do this with group by and having:
select cl.custid
from cust_lang cl join
languages l
on cl.langid = l.id
where l.language in ('English', 'Spanish', 'Portuguese')
group by cl.custid
having count(*) = 3;
If, for example, you only wanted to check for two languages, then you need only change you WHERE ... IN and HAVING conditions, e.g.:
where l.language in ('English', 'Spanish')
and
having count(*) = 2
This is pretty much Gordon's answer but it has the benefit of being a little more flexible on the language list and it doesn't require any change to the having clause.
with my_languages as (
select langId from languages
where language in ('English', 'Spanish')
)
select cl.custId
from cust_lang as cl inner join my_languages as l on l.langId = cl.langId
group by cl.custId
having count(*) = (select count(*) from lang)
I have a many-to-many relationship between my group model and my sport model with the usual group_sport table as the pivot table.
Group table
ID|Group_name
1 |Group 1
2 |Group 2
3 |Group 3
group_sport table
ID|groupID|sportID
1 |1 |1
2 |1 |2
3 |1 |3
4 |2 |2
5 |2 |4
6 |3 |5
7 |3 |6
8 |3 |4
sport table
ID|sport_name
1 |football
2 |tennis
3 |golf
4 |hockey
5 |cricket
6 |athletics
What I would like to do is display all distinct groups with their corresponding sport in the view so it would look something like this
Group 1|football, golf, tennis
Group 2|tennis, hockey
Group 3|cricket, athletics, hockey
I can achieve this by doing 3 separate queries but would there be a more efficient way?
Or what I don't mind doing is displaying all sports and ordering by group but then that means I would be displaying all sports however with their groups(the groups would be repeated which is what I don't want).
In this case would you know if JQuery could help in deleting certain elements so that my groups are not repeated?
I have a typical parent/child relationship table to represent folders. My challenge is using it in conjunction with another table.
The folder table is like this:
+--+----+--------+
|id|name|parentid|
+--+----+--------+
|1 |a |null |
+--+----+--------+
|2 |b |1 |
+--+----+--------+
|3 |c1 |2 |
+--+----+--------+
|4 |c2 |2 |
+--+----+--------+
The association table is like this:
+--+--------+
|id|folderid|
+--+--------+
|66|2 |
+--+--------+
|77|3 |
+--+--------+
so that where association.id = 66 has a relationship to folder.id = 2
What I need to do is find the association.id of the first ancestor with a record in the association table.. Using the example data above, given folder.id of 3 I expect to find 77; given folder.id of 2 or 4 I expect to find 66; any other folder.id value would find null.
Finding folder ancestry can be done with a common table expression like this:
WITH [recurse] (id,name,parentid,lvl) AS
(
select a.id,a.name,a.parentid,0 FROM folder AS a
WHERE a.id='4'
UNION ALL
select r.id,r.name,r.parentid,lvl+1 FROM folder as r
INNER JOIN [recurse] ON recurse.parentid = r.id
)
SELECT * from [recurse] ORDER BY lvl DESC
yielding the results:
+--+----+--------+---+
|id|name|parentid|lvl|
+--+----+--------+---+
|1 |a | |2 |
+--+----+--------+---+
|2 |b |1 |1 |
+--+----+--------+---+
|4 |c2 |2 |0 |
+--+----+--------+---+
To include the association.id I've tried using a LEFT JOIN in the recursive portion of the CTE, but this is not allowed by SQL Server.
What workaround do I have for this?
Or better yet, is the a way to query directly for the particular association.id? (e.g., without walking through the results of the CTE query that I have been attempting)
SELECT r.id, r.name, r.parentid, r.lvl, a.folderid, a.id as associationid
FROM [recurse] r
LEFT JOIN [association] a
ON r.id = a.folderid
WHERE a.folderId IS NOT NULL
ORDER BY lvl DESC
This will give you the records that have values in the association table. Then you could limit it to the first record that has a value or just grab the top result