Im having trouble passing a value to a subquery in MySQL, for what i have read this is not possible in MySQL, but i cant manage to find anotherway to do this query.
the value to pass is "pnl_partsA.part_image" from the first part of the query.
What Im tying to obtain is the part_image that is present in more than one manufacturer.
SELECT manufacturer, chapter, part_image
FROM pnl_parts pnl_partsA
WHERE 1 = 1
AND part_image <> ''
#AND manufacturer = 'fiat'
#AND part_image = 'F01A050'
AND ( SELECT COUNT(chapter)
FROM ( SELECT manufacturer, chapter, part_image
FROM pnl_parts
WHERE part_image = pnl_partsA.part_image
AND part_image <> ''
AND manufacturer = pnl_partsA.manufacturer
GROUP BY manufacturer, chapter, part_image
) chaptercount
) > 1
ORDER BY part_image
;
Adding more information...
What I need to get are the chapters that have a duplicate part_image
any help will be appreciated thanks.
You can get all the manufacturer and part_image group(s), which has more than one rows, using Group By and Having COUNT(*) > 1. We will use this result-set in a Derived table, and Join to the main table, to get the relevant row(s):
Try the following query instead:
SELECT
pp1.manufacturer,
pp1.chapter,
pp1.part_image
FROM pnl_parts AS pp1
JOIN (
SELECT
pp2.manufacturer,
pp2.part_image
FROM pnl_parts AS pp2
WHERE pp2.part_image <> ''
GROUP BY
pp2.manufacturer,
pp2.part_image
HAVING COUNT(*) > 1
) AS dt
ON dt.manufacturer = pp1.manufacturer AND
dt.part_image = pp1.part_image
Related
Let's say we have a person table and survey table. survey is a set of attributes collected from a person at some point in time. Let's say survey has columns address and marriage_status
How do I select all persons whose address or marriage status has changed in the last survey?
Here's how I would write it if MySQL were able to magically interpret my intention:
SELECT *
FROM person
JOIN
(SELECT *
FROM survey
GROUP BY survey.person_id
ORDER BY survey.timestamp DESC
LIMIT 2 EACH) -- of course this part doesn't actually work. Trying to get last 2 records per person
surveys
ON surveys.person_id = person.id
WHERE surveys[0].address != surveys[1].address
OR surveys[0].marriage_status != surveys[1].marriage_status;
OR
SELECT *
FROM person
JOIN
(SELECT MOST RECENT survey FOR EACH person) latest_survey
ON latest_survey.person_id = person.id
JOIN
(SELECT SECOND MOST RECENT survey FOR EACH person) previous_survey
ON previous_survey.person_id = person.id
WHERE latest_survey.address != previous_survey.address
OR latest_survey.marriage_status != previous_survey.marriage_status;
This seems like a relatively straightforward query, but it's driving me crazy. I suspect I have tunnel vision and I'm not approaching this the right way.
EDIT: I am on MySQL v5. Based on the first couple answers, it seems like this might be the time to migrate to v8 (among other reasons)
So here's how I ended up doing it. It's a little long, but I think it's pretty straightforward? This felt amazing to get working.
(Note that underscores are used as prefixes in table aliases to help keep track of subquery depth)
SELECT person.*
FROM person
JOIN (
-- Join full survey data against each 'most recent' survey timestamp
SELECT s1.*
FROM survey s1
JOIN (
-- get most recent timestamp for each person
SELECT _s1.person_id, MAX(_s1.timestamp) timestamp
FROM survey _s1
GROUP BY person_id
) latest_surveys
ON latest_surveys.person_id = s1.person_id and latest_surveys.timestamp = s1.timestamp
) latest
ON latest.person_id = person.id
JOIN (
-- Join full survey data against each 'SECOND most recent' survey timestamp
select s2.*
from survey s2
JOIN (
-- to get SECOND most recent survey timestamp, do similar query, but exclude latest timestamp
SELECT _s2.person_id, MAX(_s2.timestamp) timestamp
FROM survey _s2
JOIN (
-- get most recent timestamp for each person (again)
SELECT __s2.person_id, MAX(__s2.timestamp) timestamp
FROM survey __s2
GROUP BY person_id
) _latest_surveys
-- Note the *NOT* equal here
ON _latest_surveys.person_id = _s2.person_id and _latest_surveys.timestamp != _s2.timestamp
GROUP BY _s2.person_id
) previous_surveys
ON previous_surveys.person_id = s2.person_id and previous_surveys.timestamp = s2.timestamp
) previous
ON previous.person_id = person.id
WHERE latest.address != previous.address
OR latest.marriage_status != previous.marriage_status;
Analytic functions make your question much more tractable. If you are not yet using MySQL 8+, then now would be a good time to upgrade. Assuming you are using MySQL 8+, we can try:
WITH cte AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY p.id ORDER BY s.timestamp DESC) rn
FROM person p
INNER JOIN survey s ON p.id = s.person_id
)
SELECT id
FROM cte
GROUP BY id
HAVING
MAX(CASE WHEN rn = 1 THEN address END) <> MAX(CASE WHEN rn = 2 THEN address END) OR
MAX(CASE WHEN rn = 1 THEN marriage_status END) <> MAX(CASE WHEN rn = 2 THEN marriage_status END);
The above query uses a pivot trick to isolate the latest, and second latest, addresses and marriage statuses for each person. It retains person id values for those whose latest and second latest addresses or marriage statuses are not identical.
This might be how you can achieve that:
SELECT *
FROM person
JOIN (
SELECT *,
MAX(survey_date) latest_survey,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(survey_date ORDER BY person_id, survey_date ASC),',',-2),',',1) previous_survey,
SUBSTRING_INDEX(GROUP_CONCAT(address ORDER BY person_id, survey_date ASC),',',-1) curadd,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(address ORDER BY person_id, survey_date ASC),',',-2),',',1) prevadd,
SUBSTRING_INDEX(GROUP_CONCAT(marriage_status ORDER BY person_id, survey_date ASC),',',-1) curms,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(marriage_status ORDER BY person_id, survey_date ASC),',',-2),',',1) prevms
FROM survey GROUP BY person_id
HAVING curadd != prevadd OR curms != prevms) A
ON person.id=A.person_id;
Using GROUP_CONCAT and SUBSTRING_INDEX to combine the data value then separate it again and using those to compare at the end. I know there are a bunch of ways to achieve without all these, like your second example is something that I think can be done but when I think about it, it's going to be a very long query. This query however, since you're not using MySQL 8+ is much shorter but the performance of this query is a concern especially on a large table.
It is not given, but I hope you have at least MySQL 8 or similar to have ability to use Common Table Expression. It can simplify the complex query.
The trick part is getting survey records #1 and #2 for each user. I will do it this way: see cte1 and cte2 definition
WITH
cte1 AS (
SELECT MAX(x1.id) AS id, x1.person_id
FROM survey x1
GROUP BY x1.person_id),
cte2 AS (
SELECT MAX(x2.id) AS id, x2.person_id
FROM survey x2
JOIN cte1 ON cte1.person_id = x2.person_id
AND cte1.id > x2.id
GROUP BY x2.person_id)
SELECT
p.*,
s1.address, s2.address address2,
s1.marriage_status, s2.marriage_status marriage_status2
FROM person AS p
JOIN (
cte1 JOIN survey s1 ON s1.id = cte1.id
) ON cte1.person_id = p.id
JOIN (
cte2 JOIN survey s2 ON s2.id = cte2.id
) ON cte2.person_id = p.id
WHERE
(s1.address <> s2.address)
OR (s1.marriage_status <> s2.marriage_status)
https://www.db-fiddle.com/f/hLwdHiZin4MkdUZ4aBz67H/2
Update: Thanks to Ian, I replaced MIN to MAX to get recent records
I have came up with solution to count total of fields based on specific group, but it looks quite lengthy to get to the result i expect.
I have some basic knowledge when it comes to sql.
Is there obvious improvements to be made and why?
Why i would like to shorten this: Easier to implement in ORM type systems.
Changing scheme is not an option.
Schema and sample data: http://sqlfiddle.com/#!9/62df6
Query i'm using:
SELECT s.release_id,
(s.shipments_total - IFNULL(sh.shipment_entries, 0)) AS shipments_left
FROM
( SELECT release_id,
SUM(shipments) AS shipments_total
FROM subscriptions
WHERE is_paid = 1
AND shipments > 1
GROUP BY release_id ) AS s
LEFT JOIN
( SELECT release_id,
COUNT(*) AS shipment_entries
FROM shipments
GROUP BY release_id ) AS sh ON s.release_id = sh.release_id
Expected result on sample data is in sqlfiddle.
If you bring the condition in-line and remove the group by, then you don't need ifnull():
SELECT s.release_id,
(SUM(s.Shipments) -
(SELECT COUNT(*)
FROM shipments sh
WHERE sh.release_id = s.release_id
)
) AS shipments_left
FROM subscriptions s
WHERE is_paid = 1 AND shipments > 1
GROUP BY s.release_id;
The subquery returns 0 if nothing matches, not NULL (with the GROUP BY, it would return NULL). I am not sure if this is easier with your ORM model. Your original version is fine from a SQL point of view.
You can bring the join inline instead:
SELECT s.release_id,
SUM(s.Shipments) - IFNULL(( SELECT COUNT(*) AS shipment_entries
FROM shipments sh
WHERE sh.release_id = s.release_id
GROUP BY sh.release_id ), 0) AS shipments_left
FROM subscriptions s
WHERE is_paid = 1
AND shipments > 1
GROUP BY s.release_id
The execution plan for this is more performant too.
I have two queries in which I would like to find their common values. I'm trying to ultimately find out what percentage of users have visited both webpages.
SELECT DISTINCT user_id
FROM table
WHERE url ='y'
ORDER BY user_id;
SELECT DISTINCT user_id
FROM table
WHERE url ='z'
ORDER BY user_id;
I've tried a
NOT IN
and a
UNION
but haven't had much luck - though I could easily be doing it wrong. I'm new.
One method is to use conditional aggregation. To get information for each user:
select user_id,
sum(url = 'y') as y_visits,
sum(url = 'z') as z_visits
from t
group by user_id;
To get the list of users, add a having clause:
having y_visits >= 1 and z_visits >- 1
To get summary information:
select y_visitor, z_visitor, count(*)
from (select user_id,
max(url = 'y') as y_visitor,
max(url = 'z') as z_visitor
from t
group by user_id
) yz
group by y_visitor, z_visitor;
To get a simple percentage:
select avg(y_visitor = 1 and z_visitor = 1) as p_VisitedBothYandZ
from (select user_id,
max(url = 'y') as y_visitor,
max(url = 'z') as z_visitor
from t
group by url
) yz;
I'm hoping someone fluent in MySQL will be able to assist me with this. I'm trying to do a select on a select on a select, but the query doesn't seem to want to complete. Any help would be greatly appreciated.
SELECT
product as pid,
leg_name as name,
dimensions as dims
FROM
pmaint
WHERE
product in (
SELECT product
FROM qb_export_items_attributes
WHERE attribute_name = 'Z'
AND product in (
SELECT product
FROM pmainT
WHERE type_ID = (
SELECT ID
FROM type
WHERE SOFTCARTCATEGORY = 'End Table Legs'
)
)
AND attribute_value <= 3.5
)
Try to use INNER JOINs instead of IN subqueries
UPD: I've edited this query according you comment. the first JOIN subquery output all product where both attributes exists and true.
SELECT
pmaint.product as pid,
pmaint.leg_name as name,
pmaint.dimensions as dims
FROM
pmaint
JOIN (select product from qb_export_items_attributes
where ((attribute_name = 'Z') and (attribute_value <= 3.5))
OR
((attribute_name = 'top_square') and (attribute_value >= 4))
GROUP BY product HAVING COUNT(*)=2
)
t1 on (pmaint.product=t1.product )
JOIN type on (pmaint.type_ID=type.ID)
WHERE
type.SOFTCARTCATEGORY = 'End Table Legs'
I am trying to select a different set of results for a product depending on a product type.
So if my product should be a book I want it to look up the UPC and Artist for a normal product these details are however irrelevant and for another product I would want a completely different set of results.
SELECT CASE Product.type_id
WHEN 10 THEN (
SELECT
Product.product_id,
Product.type_id,
Product.product_name,
Product.UPC,
Product_Type.type,
CONCAT_WS(' ' , first_name, middle_name, last_name ) AS artistC
FROM Product, Product_Type, Product_ArtistAuthor
WHERE Product.type_id = Product_Type.type_id
AND Product.product_id = $pid
AND Product.artist_id = Product_ArtistAuthor.artist_id
)
ELSE (
SELECT
Product.product_id,
Product.type_id,
Product.product_name,
Product_Type.type
FROM Product, Product_Type
WHERE Product.type_id = Product_Type.type_id
AND Product.product_id = $pid
)
END
FROM Product
WHERE Product.product_id = $pid
I am not sure where I am going wrong
You Could try the other format for the case statement
CASE WHEN Product.type_id = 10
THEN
(
Select Statement
)
ELSE
(
Other select statement
)
END
FROM Product
WHERE Product.product_id = $pid
See http://msdn.microsoft.com/en-us/library/ms181765.aspx for more information.
You should avoid using nested selects and I would go as far to say you should never use them in the actual select part of your statement. You will be running that select for each row that is returned. This is a really expensive operation. Rather use joins. It is much more readable and the performance is much better.
In your case the query below should help. Note the cases statement is still there, but now it is a simple compare operation.
select
p.product_id,
p.type_id,
p.product_name,
p.type,
case p.type_id when 10 then (CONCAT_WS(' ' , first_name, middle_name, last_name )) else (null) end artistC
from
Product p
inner join Product_Type pt on
pt.type_id = p.type_id
left join Product_ArtistAuthor paa on
paa.artist_id = p.artist_id
where
p.product_id = $pid
I used a left join since I don't know the business logic.
For a start the first select has 6 columns and the second has 4 columns. Perhaps make both have the same number of columns (adding nulls?).
I ended up leaving the common properties from the SELECT queries and making a second SELECT query later on in the page. I used a php IF command to call for different scripts depending on the first SELECT query, the scripts contained the second SELECT query.