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I am trying to find the mutual friends with SQL from a single table
I have a simple table with 2 fields user, friends as int. Data values as are as below
Expected Output
user friend mutual friends
1 2 2
1 3 1
This is the query i tried
select ex1.user,ex2.friend, count(distinct ex3.friend) from (select distinct user from exer1) ex1
join exer1 ex2, exer1 ex3
where ex1.user=ex2.user and
ex2.user<>ex3.user and ex2.friend<>ex3.friend
group by ex1.user,ex2.friend order by 1,2
The output i got was
enter image description here
The desired output I am looking for is
enter image description here
You can use a self-join and aggregation:
select f1.user, f2.user, count(*)
from friends f1 join
friends f2
on f1.friend = f2.friend and
f1.user < f2.user
group by f1.user, f2.user;
Related
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I have a payment table. Type 1 is new/first payment. Type 11 is renew payment. So each user should have one record of type 1. But due to bad coding, right now, some records have only renew records. I want to find all the records that are missing the type 1 record. In the example below, it should return user 3.
user type amount
1 1 10
1 11 10
2 1 10
3 11 10
How should I write the query?
One way to find all users in the table that don't have a record of Type 1 is a NOT EXISTS using a subquery, as follows:
SELECT p.[user]
FROM payment p
WHERE NOT EXISTS (
SELECT 1
FROM payment
WHERE `user` = p.[user]
AND type = 1)
Alternatively, this can be done with a LEFT JOIN and only selecting the non-matching rows:
SELECT p.[user]
FROM payment p
LEFT JOIN payment p2
ON p2.[user] = p.[user]
AND p2.type = 1
WHERE p2.[user] IS NULL
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MYSQL how to increment column count if different combination row exist
for example if table have
count user certNo
0 a 001
0 b 886
if same user with different certNo comes then i need to increment count by 1,
like
count user certNo
0 a 001
0 b 886
1 a 673
For legacy MySQL version you can use next query:
select
t.*,
count(t1.certNo) as count
from test t
left join test t1 on t1.user = t.user and t1.certNo < t.certNo
group by t.user, t.certNo;
Test it on SQLize.online
You can use row number():
select row_number() over (partition by user order by certNo) - 1 as count,
user, certNo
from t;
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lists table
id user_id list_name
1 1 test
2 1 test2
items table
id list_id item_name price_item item_checked
1 1 apple 2 0
2 2 orange 2 0
result should be
id item_name price_item item_checked
1 Apple 2 0
How would i accomplish to select all from list 1
Your question is not clear but I will try my best to answer it.
To get the results you have posted:
select *
from Items_Table
Title says select all from a different table. I assume lists is the first table and items is the "different" table you are referring to.
Select Items.*
from Lists_Table Lists
left join Items_Table Items on Items.list_id = Lists.id
Now, lets assume you were looking for specific items, say where Id is 1 in the lists table. Then you would have the following:
Select Items.*
from Lists_Table Lists
left join Items_Table Items on Items.list_id = Lists.id
where Lists.id = 1
You can replace Lists.id in the where statement with any other column and set it equal to value you are looking for.
I hope this was helpful. Please try to be a bit more clear about what you are looking for!
Good Luck!
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student(sID,sNAME,sCLASS);
result(sID,subMARKS);
Actually, in MS-ACCESS, i am trying to this with equi join but getting wrong result. i'm writting my query like
SELECT stud.sID
, stud.sNAME
, stud.sCLASS
, result.sID
FROM student
, result
WHERE(SELECT MAX(subMARKS) FROM result)
It should display Ali record only because he is having maximum marks. but i am getting this kind of output as shown in picture below.
sID sNAME sCLASS
1 Ali BSC
2 Ahmad FSC
3 Asgar ICS
4 Akram BSC
SELECT T1.SID, T1.sname FROM student T1
LEFT JOIN resultT2 ON t1.sid=t2.sid
WHERE t2.submarks = (SELECT Max(submarks) FROM result);
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I have this kind of table selected from database:
user project role
XXX p1 admin
XXX p2 developer
xxx p1 developer
yyy p3 tester
yyy p1 developer
yyy p1 admin
zzz p2 developer
and I need to add to this query filter: if user has at lease two roles in one project.
How can I do that? What MySQL functions can help me in this case?
GROUP BY project and add an HAVING clause to restrict to those with COUNT > 1
SELECT user, project, count(*) AS number_of_roles
FROM thetable
GROUP BY project
HAVING count(*) > 1
Bonus: a column with all roles aggregated
SELECT user, project, count(*) AS number_of_roles, GROUP_CONCAT(role) AS roles
FROM thetable
GROUP BY project
HAVING count(*) > 1