I have the following:
SELECT id, name, job_id, job_type, job_name, updated_at
FROM
(SELECT service.id,service.service_name FROM services as service
INNER JOIN positions p ON service.id = p.service_id
) As Tab1
INNER JOIN
(SELECT job.job_id, job.job_type, job.job_name, job.updated_at
FROM jobs as job
INNER JOIN positions p ON job.id = p.job_id
) AS Tab2
How can i remove duplicates created by INNER JOIN i tired with DISTINCT but its not working correct.
positions Table has only two rows this table is my middle table:
INSERT INTO `positions` (`id`, `service_id`, `job_id`) VALUES
(1, 440, 25),
(2, 439, 63);
You made a sbselect of the second inner join, and the join with the subselect has no join cirteria
SELECT id, name, job_id, job_type, job_name, updated_at
FROM
(SELECT service.id,service.service_name FROM services as service
INNER JOIN positions p ON service.id = p.service_id
) As Tab1
INNER JOIN -- this join has no join cirteria
(SELECT job.job_id, job.job_type, job.job_name, job.updated_at
FROM jobs as job
INNER JOIN positions p ON job.id = p.job_id
) AS Tab2
You don't need the subselects in the first place, try somthing like
SELECT service.id, service.name, job_id, job_type, job_name, updated_at
FROM
services as service
INNER JOIN positions p ON service.id = p.service_id
INNER JOIN jobs as job ON job.id = p.job_id
The problem is that you are joining the two subquery tables with no clause (ON field1 = field2).
You are pulling the id from the first table and the other fields from the second, with no connecting clause between the table. That is why you are getting partially duplicated data.
You need to add the joining clause between the tables.
I am not going to assume that you can do so logically by joining on the job_id, as was previously suggested. This would require that the two tables share specific job_ids. Of course, if this is true, then you just add the ON tab1.job_id = tab2.job_id and you should not see the same duplicated data.
You did not provide the data from the other tables, so I cannot tell if you would still get duplicates, as it would depend on if the same job_id appears in the tables more than once. To clear that up, you can do a DISTINCT or GROUP BY on all the fields to make the results unique. The fact that you said you tried distinct seems to confirm that you need the joining clause.
If you cannot join by job_id as it does not logically link the two tables, you will need to provide more logic into what you think the data should look like.
Related
Iam currently trying to left join a table on a left joined table as follows.
I have the tables:
accounts (id, vorname, nachname)
projektkurse (id, accounts_id, projektwochen_id)
projektkurs_einzel (id, projektkurse_id)
projektkurs_einzel_zeiten (id, date, shift, projektkurs_einzel_id)
Now I want to get every account and the amount times they have an entry inside of projektkurs_einzel_zeiten, which should also be unique. So having the same date and shift multiple times does not count as multiple entries. The result should also be limited by the column projektwochen_id from the table projektkurse. This column should match a certain value for example 8.
Some Accounts don't have any entries in projektkurse, projektkurs_einzel and projektkurs_einzel_zeiten, this is why my first thought was using LEFT JOIN like this:
SELECT accounts.id, accounts.vorname, accounts.nachname, COUNT(DISTINCT projektkurs_einzel_zeiten.date, projektkurs_einzel_zeiten.shift) AS T
FROM accounts
LEFT JOIN projektkurse on accounts.id = projektkurse.creator_id
LEFT JOIN projektkurs_einzel on projektkurse.id = projektkurs_einzel.projektkurs_id
LEFT JOIN projektkurs_einzel_zeiten ON projektkurs_einzel.id = projektkurs_einzel_zeiten.projektkurs_einzel_id
WHERE projektkurse.projektwochen_id = 8
GROUP BY accounts.id
This query does not achieve exactly what I want. It only returns accounts that have atleast one entry in projektkurse even if they have none in projektkurs_einzel and projektkurs_einzel_zeiten. The Count is obviously 0 for them but the accounts that have no entries in projektkurse are being ignored completly.
How can I also show the accounts that don't have entries in any other table with the Count 0 aswell?
I would recommend writing the query like this:
SELECT a.id, a.vorname, a.nachname,
COUNT(DISTINCT pez.date, pez.shift) AS T
FROM accounts a LEFT JOIN
projektkurse
ON a.id = pk.creator_id AND
pk.projektwochen_id = 8 LEFT JOIN
projektkurs_einzel pe
ON pk.id = pe.projektkurs_id LEFT JOIN
projektkurs_einzel_zeiten pez
ON pe.id = pez.projektkurs_einzel_id
GROUP BY a.id, a.vorname, a.nachname;
Notes:
Your problem is fixed by moving the WHERE condition to the ON clause. Your WHERE turns the outer join into an inner join, because NULL values do not match.
Table aliases make the query easier to write and to read.
It is a best practice to include all unaggregated columns in the GROUP BY. However, assuming that id is unique, your formulation is okay (due to something called "functional dependencies").
You should not use eft join table's column ins where condition this work as inner join
You should move the where condition for a left joined table in the corresponding ON clause
SELECT accounts.id, accounts.vorname, accounts.nachname, COUNT(DISTINCT projektkurs_einzel_zeiten.date, projektkurs_einzel_zeiten.shift) AS T
FROM accounts
LEFT JOIN projektkurse on accounts.id = projektkurse.creator_id
AND projektkurse.projektwochen_id = 8
LEFT JOIN projektkurs_einzel on projektkurse.id = projektkurs_einzel.projektkurs_id
LEFT JOIN projektkurs_einzel_zeiten ON projektkurs_einzel.id = projektkurs_einzel_zeiten.projektkurs_einzel_id
GROUP BY accounts.id
I have some problem with the query issue when trying to sum up the quantity.
Table
This cart item table stored id_cart and id product
This order table stored id_cart and other id may be included such as supplier. This table is used to track order record and send notification to supplier.
Wrong result. Expected output = 1, 1, 1
SELECT id, id_product, SUM(qty)
from cart_item
left join Orderp using(id_cart)
group by id_product
http://sqlfiddle.com/#!9/07bf57/1
The issue caused by duplicate id_cart in order table as well. How can i handle this? Any solution to make it works? Thanks.
There is something wrong in your data, or in your data model
INSERT INTO OrderP(`id_order`,`id_cart`)VALUES(1, 1);
INSERT INTO OrderP(`id_order`,`id_cart`)VALUES(2, 1);
There are 2 rows for id_cart = 1, so the "natural join" will double every row when joining cart_item to orderp.
Using an inner join to a different column in orderp works better because now there is only one row in orederp for each cart_item.
SELECT id_product, sum(qty)
from cart_item ci
left join Orderp o on ci.id_cart = o.id_order
GROUP BY id_product
http://sqlfiddle.com/#!9/07bf57/13
Try the following query
SELECT
i.id_product,
p.name productname,
b.id_branch,
b.branchname,
SUM(i.qty)
from cart_item i
left join (SELECT DISTINCT id_cart,id_branch FROM Orderp) o on o.id_cart=i.id_cart
left join product p on i.id_product=p.id_product
left join catalog c on c.id_product=p.id_product and c.id_branch=o.id_branch
left join branch b on b.id_branch=o.id_branch
group by
i.id_product,
p.name,
b.id_branch,
b.branchname
The main problem in Orderp table because it containts two different orders for one cart (DISTINCT id_cart,id_branch helps here). And you need to use the second condition by id_branch for catalog (and c.id_branch=o.id_branch).
SQL Fiddle - http://sqlfiddle.com/#!9/f32d5f/16
And I think you can use everywhere INNER JOIN instead LEFT JOIN
SELECT
i.id_product,
p.name productname,
b.id_branch,
b.branchname,
SUM(i.qty)
from cart_item i
join (SELECT DISTINCT id_cart,id_branch FROM Orderp) o on o.id_cart=i.id_cart
join product p on i.id_product=p.id_product
join catalog c on c.id_product=p.id_product and c.id_branch=o.id_branch
join branch b on b.id_branch=o.id_branch
group by
i.id_product,
p.name,
b.id_branch,
b.branchname
What happens actually when we use cascaded join statements
select student.name, count(teacher.id)
from student
left join course on student.course_id = course.id
left join teacher on student.teacher_id = teacher.id
group by student.name;
It seems when I used only the first left join alone it returned 30 rows while using the second left join alone returned 20 rows. But using together returns 600 rows. What is actually happening ? Does the result from the first left join is used in the second ? I don't understand the semantics. Help me understand it.
Since you don't have any join conditions between teacher and course, you're getting a full cross-product between each of the other two joins. Since one join returns 20 rows and the other returns 30 rows, the 3-way join returns 20x30 = 600 rows. Its equivalent to:
SELECT t1.name, count(t2.id)
FROM (SELECT student.name
FROM student
LEFT JOIN course ON student.id = course.id) AS t1
CROSS JOIN
(SELECT teacher.id
FROM student
LEFT JOIN teacher ON student.id = teacher.id) AS t2
GROUP BY t1.name
Notice that the CROSS JOIN of the two subqueries has no ON condition.
The correct way to structure this database is as follows:
student table: id (PK), name
course table: id (PK), name, fee, credits
student_course table: id (PK), student_id (FK), course_id (FK), unique key on (student_id, course_id)
Then to get the name of each student and the average course fee, you would do:
SELECT s.name, AVG(c.fee) AS avg_fee
FROM student AS s
LEFT JOIN student_course AS sc ON s.id = sc.student_id
LEFT JOIN course AS c ON sc.course_id = c.id
All Mysql joins are graphically explained here. Take a look and choose correct joins for both joined tables.
I have 4 tables in an existing mysql database of a directory type site.
Table mt_links contains basic info for each listing
Table mt_cl contains which listing above is in what category (I only want cat_id=1)
Table mt_cfvalues contains more details for each listing It Can have repeated values
Table mt_images contains image names for each listing.
I want all records from mt_links where the mt_cl cat_id=1, and for each of those records, I need all records in mt_cfvalues and cf_images matching the link_id.
I set up a select with Group_Concat and left joins, but ended up with repeating values in my results. I added Distinct, which cured the repeating values, but mt_cfvalues can have records with the same value, so now I'm missing a value I should have.
SELECT a.link_id,
a.link_name,
a.link_desc,
GROUP_CONCAT(DISTINCT b.value ORDER BY b.cf_ID) AS details,
GROUP_CONCAT(DISTINCT c.filename ORDER BY c.ordering) AS images
FROM mt_links a
LEFT JOIN mt_cfvalues b ON a.link_id = b.link_ID
LEFT JOIN mt_images c ON b.link_id = c.link_ID
LEFT JOIN mt_cl d ON a.link_id = d.link_ID WHERE d.cat_ID = '1'
GROUP BY a.link_id
I put together a SQLFiddle here: http://www.sqlfiddle.com/#!2/f39e9/1
Is there an easier way? How do I fix the repeating / no repeating issue?
Here is one way of accomplishing what you seek. Because the two subqueries return independent results, you can't combine the GROUP BY, which is why you were getting duplicates.
SELECT a.link_id,
a.link_name,
a.link_desc,
cvf.details,
imgs.images
FROM mt_links a
LEFT JOIN (
SELECT link_ID, GROUP_CONCAT(value ORDER BY cf_ID) AS details
FROM mt_cfvalues
GROUP BY link_ID
) cvf ON cvf.link_ID = a.link_id
LEFT JOIN (
SELECT link_ID, GROUP_CONCAT(filename ORDER BY ordering) AS images
FROM mt_images
GROUP BY link_ID
) imgs ON imgs.link_ID = a.link_id
INNER JOIN mt_cl d ON a.link_id = d.link_ID
WHERE d.cat_ID = '1'
I have a table called "orders" with
order_id
customer_name
item
and am joining it to another table called "orders_requests" containing
order_id
requests
One row in "orders" may have zero or more rows in "order_requests." I'm trying to perform a query to find "orders" that have "orders_requests" of "rush processing" and "free shipping." I'm leaning towards a RIGHT OUTER JOIN with the "orders_requests" table on the left so it only returns results if a corresponding "orders" row exists, but I've had no success with either of these queries.
This one doesn't work since it pulls rows that are rush processing or free shipping.
SELECT DISTINCT orders.order_id, orders.* ,
FROM orders_requests
RIGHT OUTER JOIN orders ON orders_requests.order_id = orders.order_id
WHERE orders_requests.requests
IN ('rush processing', 'free shipping')
And this one clearly doesn't work since it's impossible for any one row to match both conditions.
SELECT DISTINCT orders.order_id, orders.* ,
FROM orders_requests
RIGHT OUTER JOIN orders ON orders_requests.order_id = orders.order_id
WHERE orders_requests.requests = 'rush processing'
AND orders_requests.requests = 'free shipping'
Is what I'm trying to do possible with my table setup do I need to change the structure?
I am not sure if this would work since I cannot test it atm but try this:
select a.order_id, b.*, c.*
from orders a
left outer join orders_requests b on b.order_id = a.order_id
left outer join orders_requests c on c.order_id = a.order_id
where b.requests = 'rush processing' and c.requests = 'free shipping'