Excuse any novice jibberish I may use to explain my conundrum but hopefully someone here will be able to look past that and provide me with an answer to get me unstuck.
SESSIONS
+--------+---------+----------+
| id | appID | userID |
+--------+---------+----------+
| 1 | 1 | 96 |
+--------+---------+----------+
| 2 | 2 | 97 |
+--------+---------+----------+
| 3 | 1 | 98 |
+--------+---------+----------+
USERS
+--------+---------+
| id | name |
+--------+---------+
| 96 | Bob |
+--------+---------+
| 97 | Tom |
+--------+---------+
| 98 | Beth |
+--------+---------+
For each session in the Sessions table that has an appID of 1, I want to get the users name from the Users table. The Sessions userID column is linked with the Users tables id column.
So my desired result would be:
["Bob", "Beth"]
Any suggestions/help?
try this:
SELECT USERS.name FROM USERS INNER JOIN SESSIONS ON users.id = SESSIONS.userID WHERE SESSIONS.appID = 1
I would read up on http://blog.codinghorror.com/a-visual-explanation-of-sql-joins/ for how all the joins work.
It looks like you forgot to post your code.
But in explanation.... It seems like you can just select the userID from the sessions table and then simply join the users table. Then create a WHERE clause to select all users that are attached to that ID.
Hope it helps.
If you post your code I can probably help you out more and if this doesnt seem just right lemme know and ill help you how i can
You need to create a join table (http://www.tutorialspoint.com/postgresql/postgresql_using_joins.htm) and then request the data using the equal operator.
SELECT USERS.name FROM USERS, SESSIONS WHERE SESSIONS.userID = USERS.ID ;
Related
I'm working on a legacy system that allowed the insertion of multiple entries with the same email. In the people table are present entries with same name and email and also different name with an already used email (es. the user didn't know or didn't ask the email address to the person and chose to put a fake one).
A person could subscribe to a User multiple times yearly basis
They asked me for a report of which users entered the most of these entries.
Let's say I have 3 tables
| people| | subscriptions| |users|
| ------| |--------------| |-----|
| id | | id | |id |
| name | | personId | |name |
| email | | userId |
| subYear |
I found all duplicate emails and their occurrences using this query
SELECT users.name, people.email, count(subscriptions.id) nSub
FROM people
INNER JOIN (SELECT email, count(id) occurrences
FROM people
where email is not null and email != ""
GROUP BY email
HAVING occurrences > 1) duplicates
ON people.email = duplicates.email
JOIN subscriptions ON people.id = subscriptions.personId
JOIN users on users.id = subscriptions.userId
group by users.name, people.email;
but now I'm stuck when I have to integrate users, the query gives incorrect results or gets stuck in a loop.
I'm sure I'm getting the grouping wrong but I got lost
The result I'm trying to achieve is something like (based on data provided in fiddle)
|users.name| people.email | occurrences |
|----------|-------------------------|-------------|
| User1 | example#example.com | 1 |
| User2 | example#example.com | 2 |
| User2 | fake#email.com | 3 |
| User3 | fake#email.com | 1 |
Any suggestion you can give me is welcome. Thank's in advance
UPDATE: Sorry for the sloppiness, I created a fiddle
sql-fiddle
I'm lost here :)
I need to limit the number of times a user appears in the results of a select query.
Let's consider this two tables:
user
+------------+-----------+----------+---------------------+
| user_id | firstname | lastname | max_articles |
+------------+-----------+----------+---------------------+
| u01 | Yusuf | Shakeel | 2 |
| u02 | John | Doe | 6 |
| u03 | Jane | Doe | 4 |
+------------+-----------+----------+---------------------+
articles
+------------+-----------+-----------+
| article_id | user_id | content |
+------------+-----------+-----------+
| art01 | u01 | BláBláBlá |
| art02 | u01 | BláBláBlá |
| art03 | u03 | BláBláBlá |
| art04 | u03 | BláBláBlá |
| art05 | u02 | BláBláBlá |
| art06 | u01 | BláBláBlá |
+------------+-----------+-----------+
In user table there is the max articles that can appear for each user.
So when i do:
SELECT * FROM articles
It will list all articles. As you can see user u01 has 3 articles, but it just can appear 2 articles based on user table info.
What i need is to select all articles but limit the number of articles for each user depending on user.max_articles
Is this possible? How can i solve this?
I hope I have been able to explain what I mean.
I am using MySql.
Thank you all very much.
P.S. - I edited almost everything. Thank you.
EDIT
The select query should consider the two tables. Something like this:
SELECT articles.* FROM articles
LEFT JOIN user ON user.user_id = articles.user_id
So some how it should count the results that are being listed for each user and compare it with user.max_articles If it is >= it keeps listing results except from that user - it should do this for each user while listing.
How can this be done?
Thank you very much.
Try this and let me know if the result is anywhere close to what you're trying to achieve:
SELECT articles.user_id,
-- 1st operation
COUNT(ARTICLE_ID) AS op1,
-- 2nd operation
MAX(ARTICLE_ID) AS op2,
-- 3rd operation
IF(COUNT(ARTICLE_ID) >= MAX_ARTICLES, COUNT(ARTICLE_ID),'') AS op3,
MAX_ARTICLES
FROM articles
LEFT JOIN USER ON user.user_id = articles.user_id
GROUP BY USER.USER_ID;
I have two tables "contacts" and "users". Users table storing data with "," separated. Need to distinct data in "Contacts" column from "Contacts" table. And need to join with "Users" table, and get the records.
Contacts Table
--------------------------
id | user_Id | contats
--------------------------
1 | 2147483647 | 90123456789,90123456789,90123456789,90123456789
2 | 2147483647 | 90123456789,90123456789,90123456789,90123456789
3 | 919444894154 | 90123456789,90123456789,90123456789,90123456789
Users Table
-----------------------------
id | username | email | phone
-----------------------------
1 | bhavan | bhavanram93#gmail.com | 90123456789
2 | bhavan | bhavanram93#gmail.com | 90123456789
3 | prince | prince#gmail.com | 1234567980
4 | bhavan | bhavanram93#gmail.com | 90123456789
5 | hello | hello#gmail.com | 1234567890
6 | bhavan | bhavanram93#gmail.com | 90123456789
Your table Contacts shouldn't be constructed this way.
Since you want 1 Users table containing all the data about a user, and 1 Contacts table containing links between different users, you'd rather do this kind of table structure :
Contacts table
id | user_id | contact_id
-------------------------
1 | 1 | 2
2 | 1 | 3
3 | 2 | 3
That'll allow you to do something like :
SELECT *
FROM Users
JOIN Contacts ON (Users.id = Contacts.contact_id)
WHERE Contacts.user_id = 1
Which will return all the data of the contacts of the user 1.
Your current structure is a huge ongoing mess, it's the opposite of being flexible.
You should restructure your db to a normalized format as Steve suggest.
But if you cant:
SELECT *
FROM Users
JOIN Contacts
ON CONCAT(',', Contacts.contacts, ',') like
CONCAT('%,', Users.phone, ',%')
WHERE Contacts.user_id = 1
the idea is you convert your contacts to
, <numbers> ,
,90123456789,90123456789,90123456789,90123456789,
and try to match with
%,90123456789,%
Note this approach cant use any index so will have bad performance with many
rows. if you are in the order of 1k-10k rows may be ok. More than that you need consider restructure your db.
I'm quite a beginner in MySQL I just know the totally basic statements, however now I'ts time for me to get into some more difficult, but worth stuff.
I actually have 3 tables in MySQL, here is the representation:
users:
user_id | name | country
---------------------------
1 | Joseph | US
2 | Kennedy | US
3 | Dale | UK
admins:
admin_id | name | country
----------------------------
1 | David | UK
2 | Ryan | US
3 | Paul | UK
notes:
id | n_id | note | comment | country | type | manager
----------------------------------------------------------------
1 | 3 | This is the 1st note | First | US | admin | 2
2 | 2 | This is the 2nd note | Second | US | user | 1
3 | 2 | This is the 3rd note | Third | UK | user | 2
Now I would like to execute something like this SQL (I'm going to type not real commands here, because I'm not really familiar with all of the SQL expressions):
IF notes.type = admin
THEN
SELECT
notes.note,
notes.comment,
notes.country,
admins.name,
admins.country
FROM notes, admins
WHERE notes.n_id = admin.admin_id
ELSEIF notes.type = 'user'
SELECT
notes.note,
notes.comment,
notes.country,
users.name,
users.country
FROM notes, users
WHERE notes.n_id = users.user_id
I hope you understand what would I like to achieve here. I could do this easily with more SQL statements, but I would like to try some query which doesn't use that much resources.
Edit 1:
I would like to Get all of the Notes and get which usergroup has submitted it than apply the user's name to it. I mean, if the admin submitted the note, than SQL should choose the ID from the Admin table (as per the type value) but if a User submitted the note, it should get the name from the Users table.
The result should look something similar to this:
result:
------
id | note | comment | country | name
--------------------------------------------------------
1 | This is the 1st note | First | US | Paul
2 | This is the 2nd note | Second | US | Kennedy
3 | This is the 3rd note | Third | UK | Kennedy
Edit 2:
I have actually forgot to mention, that all of these should be listed to a manager. So a 'manager ID' should be added to the Notes and list all of the notes where the manager is for example: 2.
Here is a method that you can do in one query:
SELECT n.note, n.comment, n.country,
coalesce(a.name, u.name) as name, coalesce(a.country, u.country) as country
FROM notes n left join
admins a
on n.n_id = a.admin_id and n.type = 'admin' left join
users u
on n.n_id = u.user_id and n.type = 'user';
This uses left join to bring the records together from both tables. It then chooses the matching record for the select.
To select a particular manager, remove the semicolon and add:
where n.manager = 2;
If you expect admins and users in one result you have got several options. The simplest way is to make a union select like this:
SELECT
notes.note,
notes.comment,
notes.country,
admins.name,
admins.country
FROM
notes join admins on notes.n_id = admin.admin_id
WHERE
notes.manager = 2
UNION ALL
SELECT
notes.note,
notes.comment,
notes.country,
users.name,
users.country
FROM
notes join users on notes.n_id = users.user_id
WHERE
notes.manager = 2
I have two MySql tables:
users(id_user, name, age, gender ).
ways(#id_user,id_way, start, end, date).
What I want is to retrieve all the ways with their corresponding users details.
So my result would be like this:
id_way | start | end | date | id_user | name | age | gender
---------------------------------------------------------------------------
2 | place1 | place2 | 12/06/2013 | 145 | john | 28 | m
Have you tried JOIN?
SELECT ways.id_way, ways.start, ways.end, ways.date, users.*
FROM ways JOIN users USING (id_user)