I have two tables in the sql:
client
id first
1 david
2 jenna
3 ben
rating
id clientid userid rating ratetext date
1 1 3 4 Very good 12/4/2012
2 3 6 3 Simple bla bla 5/3/2013
And i want to get all the rating for a userid
so i try something like:
SELECT rating,ratetext,date,first FROM rating r
INNER JOIN client c ON r.userid = 3;
But i always get the rows with other rows that i don't need to get. any idea what is wrong with my command?
SELECT rating, ratetext, date, first
FROM rating r INNER JOIN client c
ON r.clientid = c.id
WHERE r.userid = 3;
Presumably you want to select ratings with the explicitly specified ID, and the corresponding clients because on the clientid stored in the rating record:
SELECT rating,ratetext,date,first FROM rating r
INNER JOIN client c ON c.id = r.clientid
WHERE r.userid = 3;
Your joins should describe what two pieces of information connects the two tables. You want something along the lines of:
SELECT * FROM rating r, client c WHERE r.clientid=c.id AND r.userid=3
I believe this is what you are looking for:
SELECT r.rating, r.ratetext, r.date, c.first
FROM rating AS r
INNER JOIN client AS c
ON r.clientid = c.id
WHERE r.userid = 3
You should join on the client id columns of the two tables and then use userid in where clause to filter.
Make sure you have indexes on r.clientid and r.userid.
Related
I have i question about JOINign i have tables User and Category and Request
Id
name
surname
1
Alex
Morgan
2
Tom
Brady
3
Smith
Rowe
Category
Id
Category
1
Party
2
Football match
And now someone create request for another
Request
Id_request
Id_caller
Id_receiver
id_category
1
1
2
1
2
1
3
2
Now i want query to find all request where user 1 (Alex) is caller and get this result
Id_request
Caller_name
Caller_surname
Receiver_name
Receiver _surname
Category
1
Alex
Morgan
Tom
Brady
Party
2
Alex
Morgan
Smith
Rowe
Football match
I try with JOIN but i didn't get this result. Pls help.
You just need to join the tables and take the necessary columns.
However, you need to join the table user twice. When joining a table twice, at least one of them needs to have an alias. The query shown below uses aliases for all tables.
For example, you can do:
select
q.id_request,
c.name as caller_name,
c.surname as caller_surname,
r.name as receiver_name,
r.surname as receiver_surname,
c.category
from request q
join user c on c.id = q.id_caller
join user r on r.id = q.id_receiver -- joined user again with different alias
join category y on y.id = q.id_category
where q.id_caller = 1
You just need two joins, one for the caller and another for the receiver.
select
id_request,
uc.nm_user as "Caller_name",
uc.nm_surname as "Caller_surname",
rr.nm_user as "Receiver_name",
rr.nm_surname as "Receiver_surname",
c.nm_category
from
usr uc
join
request rc on rc.id_caller = uc.id_user
join
usr rr on rr.id_user = rc.id_receiver
join
category c on c.id_category = rc.id_category
where
uc.id_user = 1
Here is the complete example
https://www.db-fiddle.com/f/cA637bx33SFMeDtyUUNqsp/0
You need to join the User table twice with request table -
SELECT R.Id_request,
U1.Caller_name,
U1.Caller_surname,
U2.Receiver_name,
U2.Receiver_surname,
C.Category
FROM Request R
JOIN User U1 ON R.Id_caller = U1.Id
JOIN User U2 ON R.Id_receiver = U2.Id
JOIN Category C ON r.id_category = C.Id;
I have three tables named
**Student Table**
-------------
id name
-------------
1 ali
2 ahmed
3 john
4 king
**Course Table**
-------------
id name
-------------
1 physic
2 maths
3 computer
4 chemistry
**Bridge**
-------------
sid cid
-------------
1 1
1 2
1 3
1 4
2 1
2 2
3 3
3 4
4 1
4 2
Now to show the student name with the course name which he had studied like,
**Result**
---------------------------
Student Course
---------------------------
ahmed physic
ahmed maths
ahmed computer
ahmed chemistry
ali physic
ali maths
john computer
john chemistry
king physic
king maths
I build following query
select s.name as Student, c.name as Course from student s, course c join bridge b on c.id = b.cid order by s.name
But it does not return the required result...
And what would be for normalized form, if I want to find who is manager over other:
**employee**
-------------------
id name
-------------------
1 ali
2 king
3 mak
4 sam
5 jon
**manage**
--------------
mid eid
--------------
1 2
1 3
3 4
4 5
And wants to get this result:
**result**
--------------------
Manager Staff
--------------------
ali king
ali mak
mak sam
sam jon
Use ANSI syntax and it will be a lot more clear how you are joining the tables:
SELECT s.name as Student, c.name as Course
FROM student s
INNER JOIN bridge b ON s.id = b.sid
INNER JOIN course c ON b.cid = c.id
ORDER BY s.name
Simply use:
select s.name "Student", c.name "Course"
from student s, bridge b, course c
where b.sid = s.sid and b.cid = c.cid
For normalize form
select e1.name as 'Manager', e2.name as 'Staff'
from employee e1
left join manage m on m.mid = e1.id
left join employee e2 on m.eid = e2.id
SELECT *
FROM user u
JOIN user_clockits uc ON u.user_id=uc.user_id
JOIN clockits cl ON cl.clockits_id=uc.clockits_id
WHERE user_id = 158
Don't join like that. It's a really really bad practice!!! It will slow down the performance in fetching with massive data. For example, if there were 100 rows in each tables, database server have to fetch 100x100x100 = 1000000 times. It had to fetch for 1 million times. To overcome that problem, join the first two table that can fetch result in minimum possible matching(It's up to your database schema). Use that result in Subquery and then join it with the third table and fetch it. For the very first join --> 100x100= 10000 times and suppose we get 5 matching result. And then we join the third table with the result --> 5x100 = 500. Total fetch = 10000+500 = 10500 times only. And thus, the performance went up!!!
join query with three tables and we want two values from the same column we set the alias name for every table in the joins. Same table name also declare as a different names.
const sql = `select p.ID,p.purchaseamount,urs.name as
buyername,pd.productname,
pd.amount,urs1.name as sellername
from purchases p
left join products pd on p.productid=pd.ID
left join users urs on p.userid=urs.ID
left join users urs1 on pd.userid=urs1.ID`
SELECT
employees.id,
CONCAT(employees.f_name," ",employees.l_name) AS 'Full Name', genders.gender_name AS 'Sex',
depts.dept_name AS 'Team Name',
pay_grades.pay_grade_name AS 'Band',
designations.designation_name AS 'Role'
FROM employees
LEFT JOIN genders ON employees.gender_id = genders.id
LEFT JOIN depts ON employees.dept_id = depts.id
LEFT JOIN pay_grades ON employees.pay_grade_id = pay_grades.id
LEFT JOIN designations ON employees.designation_id = designations.id
ORDER BY employees.id;
You can JOIN multiple TABLES like this example above.
Just adding a point to previous answers that in MySQL we can either use
table_factor syntax
OR
joined_table syntax
mysql documentation
Table_factor example
SELECT prd.name, b.name
FROM products prd, buyers b
Joined Table example
SELECT prd.name, b.name
FROM products prd
left join buyers b on b.bid = prd.bid;
FYI: Please ignore the fact the the left join on the joined table example doesnot make much sense (in reality we would use some sort of join table to link buyer to the product table instead of saving buyerID in product table).
Query for three table join and limit set
SELECT * FROM (SELECT t1.follower_userid, t2.*, t3.login_thumb, t3.login_name,
t3.bio, t3.account_status, t3.gender
FROM videos t2
LEFT JOIN follower t1
ON t1.follower_userid = t2.user_id
LEFT JOIN videos_user t3
ON t1.follower_userid = t3.login_userid
WHERE t1.following_userid='$userid'
LIMIT $startpoint , $limit) AS ID
ORDER BY ID DESC
Query to join more than two tables:
SELECT ops.field_id, ops.option_id, ops.label
FROM engine4_user_fields_maps AS map
JOIN engine4_user_fields_meta AS meta ON map.`child_id` = meta.field_id
JOIN engine4_user_fields_options AS ops ON map.child_id = ops.field_id
WHERE map.option_id =39 AND meta.type LIKE 'outcomeresult' LIMIT 0 , 30
Use this:
SELECT s.name AS Student, c.name AS Course
FROM student s
LEFT JOIN (bridge b CROSS JOIN course c)
ON (s.id = b.sid AND b.cid = c.id);
I have three tables named
**Student Table**
-------------
id name
-------------
1 ali
2 ahmed
3 john
4 king
**Course Table**
-------------
id name
-------------
1 physic
2 maths
3 computer
4 chemistry
**Bridge**
-------------
sid cid
-------------
1 1
1 2
1 3
1 4
2 1
2 2
3 3
3 4
4 1
4 2
Now to show the student name with the course name which he had studied like,
**Result**
---------------------------
Student Course
---------------------------
ahmed physic
ahmed maths
ahmed computer
ahmed chemistry
ali physic
ali maths
john computer
john chemistry
king physic
king maths
I build following query
select s.name as Student, c.name as Course from student s, course c join bridge b on c.id = b.cid order by s.name
But it does not return the required result...
And what would be for normalized form, if I want to find who is manager over other:
**employee**
-------------------
id name
-------------------
1 ali
2 king
3 mak
4 sam
5 jon
**manage**
--------------
mid eid
--------------
1 2
1 3
3 4
4 5
And wants to get this result:
**result**
--------------------
Manager Staff
--------------------
ali king
ali mak
mak sam
sam jon
Use ANSI syntax and it will be a lot more clear how you are joining the tables:
SELECT s.name as Student, c.name as Course
FROM student s
INNER JOIN bridge b ON s.id = b.sid
INNER JOIN course c ON b.cid = c.id
ORDER BY s.name
Simply use:
select s.name "Student", c.name "Course"
from student s, bridge b, course c
where b.sid = s.sid and b.cid = c.cid
For normalize form
select e1.name as 'Manager', e2.name as 'Staff'
from employee e1
left join manage m on m.mid = e1.id
left join employee e2 on m.eid = e2.id
SELECT *
FROM user u
JOIN user_clockits uc ON u.user_id=uc.user_id
JOIN clockits cl ON cl.clockits_id=uc.clockits_id
WHERE user_id = 158
Don't join like that. It's a really really bad practice!!! It will slow down the performance in fetching with massive data. For example, if there were 100 rows in each tables, database server have to fetch 100x100x100 = 1000000 times. It had to fetch for 1 million times. To overcome that problem, join the first two table that can fetch result in minimum possible matching(It's up to your database schema). Use that result in Subquery and then join it with the third table and fetch it. For the very first join --> 100x100= 10000 times and suppose we get 5 matching result. And then we join the third table with the result --> 5x100 = 500. Total fetch = 10000+500 = 10500 times only. And thus, the performance went up!!!
join query with three tables and we want two values from the same column we set the alias name for every table in the joins. Same table name also declare as a different names.
const sql = `select p.ID,p.purchaseamount,urs.name as
buyername,pd.productname,
pd.amount,urs1.name as sellername
from purchases p
left join products pd on p.productid=pd.ID
left join users urs on p.userid=urs.ID
left join users urs1 on pd.userid=urs1.ID`
SELECT
employees.id,
CONCAT(employees.f_name," ",employees.l_name) AS 'Full Name', genders.gender_name AS 'Sex',
depts.dept_name AS 'Team Name',
pay_grades.pay_grade_name AS 'Band',
designations.designation_name AS 'Role'
FROM employees
LEFT JOIN genders ON employees.gender_id = genders.id
LEFT JOIN depts ON employees.dept_id = depts.id
LEFT JOIN pay_grades ON employees.pay_grade_id = pay_grades.id
LEFT JOIN designations ON employees.designation_id = designations.id
ORDER BY employees.id;
You can JOIN multiple TABLES like this example above.
Just adding a point to previous answers that in MySQL we can either use
table_factor syntax
OR
joined_table syntax
mysql documentation
Table_factor example
SELECT prd.name, b.name
FROM products prd, buyers b
Joined Table example
SELECT prd.name, b.name
FROM products prd
left join buyers b on b.bid = prd.bid;
FYI: Please ignore the fact the the left join on the joined table example doesnot make much sense (in reality we would use some sort of join table to link buyer to the product table instead of saving buyerID in product table).
Query for three table join and limit set
SELECT * FROM (SELECT t1.follower_userid, t2.*, t3.login_thumb, t3.login_name,
t3.bio, t3.account_status, t3.gender
FROM videos t2
LEFT JOIN follower t1
ON t1.follower_userid = t2.user_id
LEFT JOIN videos_user t3
ON t1.follower_userid = t3.login_userid
WHERE t1.following_userid='$userid'
LIMIT $startpoint , $limit) AS ID
ORDER BY ID DESC
Query to join more than two tables:
SELECT ops.field_id, ops.option_id, ops.label
FROM engine4_user_fields_maps AS map
JOIN engine4_user_fields_meta AS meta ON map.`child_id` = meta.field_id
JOIN engine4_user_fields_options AS ops ON map.child_id = ops.field_id
WHERE map.option_id =39 AND meta.type LIKE 'outcomeresult' LIMIT 0 , 30
Use this:
SELECT s.name AS Student, c.name AS Course
FROM student s
LEFT JOIN (bridge b CROSS JOIN course c)
ON (s.id = b.sid AND b.cid = c.id);
I have two tables: DATA and USERS
USERS
id sqft postal province city
==========================================================
1 1 Y7R BC Vancouver
2 2 Y7R BC Vancouver
3 1 L5B ON Toronto
and
DATA
id uid power
=======================
1 1 1000
2 2 1300
3 1 1500
uid in table DATA matches to id in table USERS
I want to be able to count the the number of distinct uid in DATA where the postal code is Y7R and sqft is 1
SELECT COUNT(id)
FROM `DATA` AS `d`
INNER JOIN `USERS` AS `u`
ON u.id=d.uid
WHERE u.postal='Y7R' AND u.sqft=1
GROUP BY u.id;
They should be distinct anyway if you have a proper schema, if so just remove the group by clause.
SELECT COUNT(DISTINCT D.UID) FROM DATA D
LEFT JOIN USERS U ON D.UID=U.ID
WHERE U.POSTAL='Y7R' AND U.SQFT=1)
In case you need distinct
You can use this solution:
SELECT COUNT(DISTINCT a.id)
FROM USERS a
JOIN DATA b ON a.id = b.uid
WHERE a.sqft = 1 AND
a.postal = 'Y7R'
Try this one:
SELECT COUNT(DISTINCT a.id)
FROM USERS a
INNER JOIN DATA b
ON a.id = b.uid
WHERE a.sqft = 1 AND
a.postal = 'Y7R'
I'm working on a mysql query in a Drupal database that pulls together users and two different cck content types. I know people ask for help with groupwise maximum queries all the time... I've done my best but I need help.
This is what I have so far:
# the artists
SELECT
users.uid,
users.name AS username,
n1.title AS artist_name
FROM users
LEFT JOIN users_roles ur
ON users.uid=ur.uid
INNER JOIN role r
ON ur.rid=r.rid
AND r.name='artist'
LEFT JOIN node n1
ON n1.uid = users.uid
AND n1.type = 'submission'
WHERE users.status = 1
ORDER BY users.name;
This gives me data that looks like:
uid username artist_name
1 foo Joe the Plumber
2 bar Jane Doe
3 baz The Tooth Fairy
Also, I've got this query:
# artwork
SELECT
n.nid,
n.uid,
a.field_order_value
FROM node n
LEFT JOIN content_type_artwork a
ON n.nid = a.nid
WHERE n.type = 'artwork'
ORDER BY n.uid, a.field_order_value;
Which gives me data like this:
nid uid field_order_value
1 1 1
2 1 3
3 1 2
4 2 NULL
5 3 1
6 3 1
Additional relevant info:
nid is the primary key for an Artwork
every Artist has one or more Artworks
valid data for field_order_value is NULL, 1, 2, 3, or 4
field_order_value is not necessarily unique per Artist - an Artist could have 4 Artworks all with field_order_value = 1.
What I want is the row with the minimum field_order_value from my second query joined with the artist information from the first query. In cases where the field_order_value is not valuable information (either because the Artist has used duplicate values among their Artworks or left that field NULL), I would like the row with the minimum nid from the second query.
The Solution
Using divide and conquer as a strategy and mysql views as a technique, and referencing this article about groupwise maximum queries, I solved my problem.
Create the View
# artists and artworks all in one table
CREATE VIEW artists_artwork AS
SELECT
users.uid,
users.name AS artist,
COALESCE(n1.title, 'Not Yet Entered') AS artist_name,
n2.nid,
a.field_image_fid,
COALESCE(a.field_order_value, 1) AS field_order_value
FROM users
LEFT JOIN users_roles ur
ON users.uid=ur.uid
INNER JOIN role r
ON ur.rid=r.rid
AND r.name='artist'
LEFT JOIN node n1
ON n1.uid = users.uid
AND n1.type = 'submission'
LEFT JOIN node n2
ON n2.uid = users.uid
AND n2.type = 'artwork'
LEFT JOIN content_type_artwork a ON n2.nid = a.nid
WHERE users.status = 1;
Query the View
SELECT
a2.uid,
a2.artist,
a2.artist_name,
a2.nid,
a2.field_image_fid,
a2.field_order_value
FROM (
SELECT
uid,
MIN(field_order_value) AS field_order_value
FROM artists_artwork
GROUP BY uid
) a1
JOIN artists_artwork a2
ON a2.nid = (
SELECT
nid
FROM artists_artwork a
WHERE a.uid = a1.uid
AND a.field_order_value = a1.field_order_value
ORDER BY
uid ASC, field_order_value ASC, nid ASC
LIMIT 1
)
ORDER BY artist;
A simple solution to this can be to create views in your database that can then be joined together. This is especially useful if you often want to see the intermediate data in the same way in some other place. While it is possible to mash together the one huge query, I just take the divide and conquer approach sometimes.