I am looking for a better way of retrieving data from my sql tables.
Table 1: User data
- User Id
- User Created date
Table 2: Mapping of the user with a role
- User Id
- Role
Table 3
Role definition
Table 4 (may or may not have user data based on his activities on the site)
User data
Eg.
- User Id
- Total counts of the number of visits made on the portal
I am looking to write least amount of queries(preferably 1) to do the following
*I want to print the top users for each of the role types who have highest total count *
The output would read something like the following:
Header UserId---Rolename--Total Count
Row1 Test1 ---Staff --1293
Row2 Test2 ---Faculty --1223
Row3 Test3 ---Dean --2283928
Any suggestions?
Is this what you're looking for:
SELECT a.UserId, b.Role, c.TotalCount
FROM TABLE1 as a join Table2 as b on a.UserId = b.UserId
join Table 4 as c on a.UserId = c.UserId
ORDER BY c.TotalCount DESC
LIMIT 3
Related
I have 3 tables :
Person table stores basic person wise details with ID as primary Key
This person can have relationships (father / mother etc), which are saved in Relationship table, however the users for them are created in Person table (e.g. ID = 2,3 in person table), This way we know that 2,3 are related to user 1 (carry).
We also have 3rd table - address, which store user ID wise addresses.(for both a user and his related persons, who are also users)
I want to find out if an address exists for either a user or for his related users in SQL. How to achieve this ?
You can combine two rules and search on the combined table as below
SELECT * FROM
(
SELECT username,id,Address.Address
FROM Person
INNER JOIN Address ON Person.id = Address.Userid
UNION ALL
SELECT username,id,Address.Address
FROM Person
INNER JOIN Relationship ON Relationship.Relatedid = Person.id
INNER JOIN Address ON Relationship.Userid = Address.Userid
) as RES
WHERE Address = 'xyz road'
Also you can find DBFiddle link to workout
Query:
select p.id,p.username,(case when a.userid is null then 'No' else 'Yes'end) IsAddressAvailable
from Person p
left join Address a on p.id=a.Userid
Output:
id
username
IsAddressAvailable
1
Carry
Yes
2
Carry-Father
No
3
Carry-Mother
Yes
db<fiddle here
I have two tables activity_log and user_followers. I have to join these two tables and get the activity of a user with the user activity that he is following (let's say user_id 6 is following user_id 4). But the below query only returning the activity of the user having the id of 6. I want to get the activity of the user with the id of 6 plus the activity of the user he is following.
Query
SELECT activity_log.*
FROM activity_log
join user_followers ON activity_log.user_id = user_followers.follow_id
AND activity_log.user_id = 6;
activity_log:
user_followers:
Sounds like you want user_id 6's activity plus activity of users he's following. That would be:
SELECT activity_log.*
FROM activity_log
LEFT OUTER JOIN user_followers
ON activity_log.user_id = user_followers.follow_id
WHERE (activity_log.user_id = 6 OR ISNULL(user_followers.user_id,0) = 6);
The LEFT OUTER is used in case user_id 6 has no followers.
I have 2 tabes in my database:
users - userID(primary key), username, password
courses - id(primary key), name, text
subscriptions - id(primary key), curso_id, user_id
right in the subscription table I am writing the users UserID inside -> user_id with the id of the course for which he is subscribed curso_id so the results in the subscrption database are like
subscribtions table:
id user_id curso_id
1 12 1
2 5 1
3 12 2
4 6 7
this is the users table:
users table
userID username password
1 user1 passw1
2
3
4
and this is the courses table:
course table:
id course_name descriotion
1 course one text
2
3
My question is how to make a sql Query which first select the course by $row['id'] which indicates the id variable from the courses database, and after that based on the 3th table subscription to list all the users which are subscribed to this course number. ?
and second question is how to list number of the subscribed users for a course selected by
$row['id']
Here is some kind of the alghorytm logic that I have right now
SELECT * FROM users WHERE id=5.courses(select from the database 'courses') AND 5-> SELECT ALL FROM table subscriptions user_id equal to id from table users
Not sure if I understood what you try to achieve, but if you want a list that shows you every user in every course with the name of the course and ordered by course name, this should make the deal.
select t1.*, t2.*, t3.* from users as t1, courses as t2, subscriptions as t3 where t3.user_id = t1.userID and t3.curso_id = t2.id order by t2.id
Not the nicest way to do this and from a performance aspect I would recommend to put this in several statements as joins are usually slow.
okay I found the way and here is the mysql query:
FROM users
INNER JOIN subscriptions
ON users.userID = subscriptions.user_id
WHERE subscriptions.curso_id = $ids"
I'm looking to join a 2 tables but the second table has a one to many relation. Can I omit the entire row if any of the lines have a certain value? Let me explain more.
User table
id name email
1 bob bob#test.com
2 foo foo#test.com
Music table
id userId
1 1
1 2
2 1
3 1
2 2
Say I don't want it to show the user if he has a relation to music table id 2. Also looking for distinct user.
If I try something like this it will still show both users.
SELECT * FROM users u LEFT JOIN music m ON u.id = m.userId WHERE m.id <> 3
I want it to check all the rows and if it has the id 3, it won't show. I hope I made sense. Thanks a lot.
Try using sub query like this:
SELECT * FROM users
WHERE id NOT IN (SELECT userId FROM music WHERE id=3)
This query means to select all users if their id is not related with music.id 3.
I have a table, with rows of events, and each one has (amongst lots of other fields) addedbyuser, editedbyuser, deletedbyuser
There are INT, and refer back to the users table to a particular user.
I am able to join one of the fields (say addedbyuser) without any problems, how do i join the rest and reference them in php?
events table:
eventid addedbyuser editedbyuser deletedbyuser
1 1 2 3
users table:
id username
1 name1
2 name2
3 name3
So basically, I want to display the names of who added, edited and deleted the article, can I do this in one SQL query?
Something like this:
select
evn.eventid,
us1.username as addedbyuser,
us2.username as editedbyuser,
us3.username as deletedbyuser,
from events evn
join users as us1 on
evn.addedbyuser = us1.id
join users as us2 on
evn.editedbyuser = us2.id
join users as us3 on
evn.deletedbyuser = us3.id