Left Join and remove duplicates - mysql

I have three tables, clients, job_allocations and jobs table. I want to select all clients that are not in a particular job, below are my tables.
Clients table
id
Fullname
1
John Doe
2
Jane Doe
3
King James
4
Jere Gray
Jobs table
id
Title
1
Road Construction
2
Repair of Engines
job_allocations table
id
client_id
job_id
1
2
1
2
2
2
3
1
2
4
3
2
I want to select all clients that are not in job_id=2, but when I ran my query, I am getting client id: 2 - Jane Doe again, please how do I solve this?
I did this:
LEFT JOIN job_allocations ON job_allocations.client_id = clients.id
WHERE job_id <> 2 OR job_id IS NULL```

You can use a NOT IN clause as follows:
SELECT *
FROM clients
WHERE id NOT IN (SELECT client_id
FROM job_allocations
WHERE job_id = 2)
Check the demo here.

So you will fetch all clients, but only jobs related to job_id <> 2
This query should work for you:
SELECT client.*
FROM clients
LEFT JOIN job_allocations ON job_allocations.client_id = clients.id and job_id <> 2

Use DISTINCT keyword for selecting unique values

Related

MYSQL - Select row even if row does not join

I am trying to find one query that returns all people including the company they belong to and companies that do not have any person assigned yet.
Company
cid | cname
--------------
1 Company 1
2 Company 2
Person
pid | pname | fk_company
---------------------------
1 Person 1 1
2 Person 2 1
desired result
pid | pname | fk_company | cid | cname
----------------------------------------------
1 Person 1 1 1 Company 1
2 Person 2 1 1 Company 1
NULL NULL NULL 2 Company 2
Thanks in advance
If you want everything from both tables, regardless of match left AND right, you need a FULL JOIN:
SELECT *
FROM person
FULL JOIN company
ON person.fk_company = company.cid
edit: Apparently mysql doesn't support FULL JOIN. You'll have to do both LEFT JOINS by hand and UNION ALL them.
You should mention something you tried. Anyway, I will explain the method so you can work on it.
SELECT <column_names>FROM <table1_name> LEFT JOIN <table2_name>ON
<table1.column_name> = <table2.column_name>;
For more explanations please refer this link.
SQL Left Join

MySQL SQL - How to Query 2 Tables

table 1
uid email name password
----------------------------------------------
1 abc#abc.com John Doe 9q8wekdshfa
2 xyc#xyc.com Jane Doe a42adsflda2
3 me#meme.com Meme Me asd4q23llsd
table 2
id uid vocation groups
-----------------------------------
1 1 Programmer 1,3,4,5
2 2 Designer 2,4,6,8
3 3 Attorney 3
How do I write the query to get all the data about the user/s that belongs to the same group as the active logged in person. Suppose that I'm logged in as the 3rd account (me#meme.com) and I already have the data that my group is 3. How do I write the query to get this result?
uid email name password vocation groups
----------------------------------------------------------------------
1 abc#abc.com John Doe 9q8wekdshfa Programmer 1,3,4,5
You just need a basic join statement:
SELECT table1.uid, table1.email, table1.name, table1.password,
table2.vocation, table2.groups FROM table1 INNER JOIN table2 ON
table1.uid = table2.uid
WHERE table2.groups LIKE '%3%' AND email<>'me#meme.com'
And certainly read up on JOIN and basic SQL table relationships. This is database 101 stuff, that's the only reason you're getting a bit of grief in the comments and down votes.

Select unique ids from multi values on one column in another table

I'm stuck for hours on an issue that might be pretty simple to solve but I'm just so lost...
I got 3 tables :
user
id name
----------
1 jack
2 john
...
car
id name
----------
1 ford
2 fiat
3 alfa
4 lada
...
user_car
id_user id_car
-----------------
1 2
1 4
2 1
2 2
2 3
For example, i want to get all users with cars which have id 1 AND 2 in the user_car table so I should get the id_user 2 only and I can't find the proper way to do it.
try this untested query:
select * from user join user_car car1 on id =car1.user_id
join user_car car2 on id =car2.user_id where car1.id_car=1 and car2.id_car=2
I would use UNION for this matter:
SELECT id as id_user from user where id in(1, 2)
UNION
SELECT id as id_car from car where id in (1, 2)
You can use COUNT to do this:-
SELECT user.name
FROM user
INNER JOIN user_car ON user.id = user_car.id_user
INNER JOIN car ON user_car.id_car = car.id
WHERE car.id IN (1,2)
GROUP BY user.name
HAVING COUNT(DISTINCT car.id) = 2
Note that this could be simplified to remove the need for the car table when you are just using the id of the car.
May be you want this
SELECT *
FROM USER
WHERE id IN
(SELECT id_user
FROM user_car
WHERE id_car=1 OR id_car=2);

MySQL Left join with count on second Table

I have looked through some of the other posts on this site and am not seeing exactly what im looking for so here goes.
Lets say i have 2 tables
juser
-----------------------------
userID firstName lastName
-----------------------------
1 billy bob
2 jezze belle
3 bobbie sue
and:
juserrel
---------------------------------------------
id userID relUserID state
---------------------------------------------
1 1 2 approved
2 2 1 retired
3 2 1 approved
4 3 2 approved
What i am trying to do is get a result set that shows each user info about each user in the juser table and adds a column called connections to the result set which shows how many "active" connections a particular user has to another user.
the result i expect based on the tables above is
resultSet
-----------------------------------------------
userID firstName lastName connections
-----------------------------------------------
1 billy bob 2
2 jezze belle 3
3 bobbie sue 1
The query I tried is as follows
select userID, firstName, lastName , coalesce(x.cnt,0) as connections
from juser
left outer join (select count(*) cnt from juserrel where juserrel.userID =
userID or juserrel.relatedUserID = userID and juserrel.state = 'approved')
x on userID = userID
The result set i get looks like this:
resultSet
-----------------------------------------------
userID firstName lastName connections
-----------------------------------------------
1 billy bob 4
2 jezze belle 4
3 bobbie sue 4
Help Please ;)
Try:
select u.userID, u.firstName, u.lastName,
count(case when ur.state = 'approved' then 1 end)
from juser u
inner join juserrel ur on u.userID = ur.userID or u.userID = ur.relUserID
group by u.userID, u.firstName, u.lastName
SQL Fiddle Example

Query with GROUP_CONCAT not working

I have 3 tables with the following structure:
**users**
id
first_name
last_name
**specialties**
specialty_id
specialty_name
**user_specialties**
user_id
specialty_id
Here is some sample data:
**users**
1 Bill Smith
2 Tom Jones
3 Jill Hayes
**specialties**
1 word
2 web
3 database
**user_specialties**
1 1
2 1
2 3
3 2
3 3
I need to query the data so the specialties are concatinated on one row like the below output
**Desired Result**
Bill Smith word
Tom Jones word,database
Jill Hayes web,database
I am using the following query
SELECT
users.first_name,
users.last_name,
GROUP_CONCAT(specialties.specialtyname)
FROM
users
LEFT JOIN user_specialties ON user_specialties.user_id = users.userid
RIGHT JOIN specialties ON user_specialties.specialty_id = specialties.specialty_id
It is not working...
You're missing a GROUP BY clause. Most likely it should be GROUP BY users.id, and it'd go AFTER the JOIN lines.
I just tested this query
SELECT first_name,last_name,group_concat(specialty_name)
FROM user_specialties map
INNER JOIN specialties skill on user.id = map.user_id
INNER JOIN users user ON skill.specialty_id = map.specialty_id
GROUP BY user.id
Cheers! :-)