I am creating a photo ranking system. Basically, I have three main fields - won, lost, howmanyplayed.
Let's say I have three photos
Photo Won Lost Played
-------------------------
A 3 2 5
B 1 4 5
C 3 2 5
I am going to write a query to get rank of each photos. The problem is, Photo A and Photo C have exactly same record. How do make a query that returns 1 for both Photo A and C?
Photo Won Lost Played Rank
-------------------------------
A 3 2 5 1
C 3 2 5 1
B 1 4 5 ?
Added on 3/17/11
I have changed the table structure a little bit
so now I have "vote_ratio" field instead of "played". "vote_ratio" holds value of "vote_win" / "vote_lose".
so the table must be revised as
Photo Won Lost Ratio
A 3 2 1.5
B 1 4 0.25
C 3 2 1.5
What I want to do :
query only "Photo A" and get the rank of it.
query all the records and display the rank of each record.
I can do #2 by the following query.
"select * from table order by ratio desc"
but there is a problem again. Photo A and C have same ratio. I need to make both of them rank #1.
if you mean "return 1" as return 1 record of ranking ? -> not tested, however it could combination of GROUP BY and GROUP_CONCAT like this:
SELECT Won, Lost, Played, GROUP_CONCAT( photo, ', ' ) AS photos
FROM your_table
GROUP BY Won, Lost, Played
not tested
SELECT *
FROM photos
ORDER BY (played/lost)
I think it returns :
Photo A // rank1
Photo C // rank1
Photo B // rank2
Related
In my system, there should not be the same part# listed on an order more than once. I'm trying to write a query that will pull up any parts that appear on an order more than once. For example:
Order# Part QTY
1 A 1
1 A 1
1 B 5
2 A 4
2 B 4
2 C 3
3 A 5
3 B 5
3 B 7
4 A 3
4 B 6
5 A 3
So the problems here would be Order # 1 because part A appears more than once, and the same thing with Order# 3 because part B appears more than once. The rest of the orders would be fine. Where would I start if I want to achieve something like this.
The following query literally follows what you are asking. It aggregates by the combination of order and part, and returns those values when they occur more than once for a given pair.
SELECT Order, Part
FROM yourTable
GROUP BY Order, Part
HAVING COUNT(*) > 1
I did some research and learned about the COALESCE(sum(num), 0) function. The issue is the example I found only related to using one table.
I am calculating a sum from a second table, and if there are no records for an item in the second table, I still want it to show up in my query and have a sum of zero.
SELECT note.user, note.product, note.noteID, note.note, COALESCE(sum(noteTable.Score), 0) as points
FROM note, noteTable
WHERE note.user <> 3 AND note.noteID = noteTable.noteID
I am only recieving results if there is an entry in the second table noteTable. If there are scores added for a note, I still want them to show up in the result with a points value of zero.
Table Examples:
Note
user | product | noteID |note
3 1 1 Great
3 2 2 Awesome
4 1 3 Sweet
NoteTable
noteID | score
1 5
The query should show me this:
user | noteID | sum(points)
3 1 5
3 2 0
4 3 0
But I am only getting this:
user | noteID | sum(points)
3 1 5
http://sqlfiddle.com/#!9/aae812/2
SELECT
note.user,
note.product,
note.noteID, note.note,
COALESCE(sum(noteTable.Score),0) as points
FROM note
LEFT JOIN noteTable
ON note.noteID = noteTable.noteID
WHERE note.user <> 3
and I guess you should add:
GROUP BY note.noteid
if you expect to get SUM for every user. So you want to get more then 1 record back.
First, learn to use proper JOIN syntax and table aliases. The answer to your question is SUM() along with COALESCE():
SELECT n.user, n.product, n.noteID, n.note,
COALESCE(sum(nt.Score), 0) as points
FROM note n LEFT JOIN
noteTable nt
ON n.noteID = nt.noteID
WHERE n.user <> 3
GROUP BY n.user, n.product, n.noteID, n.note;
You also need a GROUP BY.
I am trying to figure out how to use the count function in order to count how many subcategories each of my categories have.
My original query is as follows(where name = the category name):
select
catid,
name,
pcatid
from category
I simply want to add a column (which is not included in my DB anywhere) called 'SubCategoryCount'. This column will count for each catid how many times it is being referenced my the pcatid column, if that makes sense.
A simple example DB would be
catid name pcatid
1 Base NULL
2 Computers 1
3 Phones 1
4 Laptops 2
5 Dell 4
And i would like to produce
catid name pcatid SubCategoryCount
1 Base NULL 2
2 Computers 1 1
3 Phones 1 0
4 Laptops 2 1
5 Dell 4 0
But how would i achive this?
Thanks for your help
John
You need to join the table itself using LEFT JOIN so it will display all records in the table even if it does not have subcategory.
SELECT a.catid,
a.NAME,
a.pcatid,
COUNT(b.pcatid) SubCategoryCount
FROM category a
LEFT JOIN category b
ON a.catid = b.pcatid
GROUP BY a.catid, a.NAME, a.pcatid
SQLFiddle Demo
PS: This query is just a projection of result without changing the original schema of the table. it doesn't physically add new column on table category.
So I have MySQL 3 tables, items (which in this case are lodging properties and the data is simplified below), amenities that the properties might offer, and amenities_index which is a list of item ids and amenity ids for each amenity offered. The end user can select any number of amenities they want and I want to return the results in order of the number of amenities that match what they are looking for. So, if they search for 3 different amenities, I want the items listed that offer all 3, then those that offer 2, 1 and finally the rest of the items. I have a query that I think is working for getting the results in the correct order, but I was hoping that I could also return a point value based on the matches, and that's where I'm running into trouble. My SQL skills are a bit lacking when it comes to more complex queries.
Here is an example query I have that returns the results in the correct order:
SELECT * FROM items
ORDER BY
(
SELECT count(*) AS points
FROM `amenities_index`
WHERE
(amenity_id = 1 || amenity_id = 2)
AND amenities_index.item_id = items.id
) DESC
And here is what the tables are structured like. Any help is appreciated.
items table
id name
1 location 1
2 location 2
3 location 3
4 location 4
amenities table
id name
1 fireplace
2 television
3 handicapped accessible
4 kitchenette
5 phone
amenities_index
item_id amenity_id
1 2
1 3
1 5
2 1
2 2
2 6
3 2
3 3
3 4
3 5
You want to move your expression into the select clause:
SELECT i.*,
(SELECT count(*) AS points
FROM `amenities_index` ai
WHERE amenity_id in (1, 2) AND
ai.item_id = i.id
) as points
FROM items i
ORDER BY points desc;
You can also do this as a join query with aggregation:
SELECT i.*, ai.points
FROM items i join
(select ai.item_id, count(*) as points
from amenities_index ai
where amenity_id in (1, 2)
) ai
on ai.item_id = i.id
ORDER BY ai.points desc;
In most databases, I would prefer this version over the first one. However, MySQL would allow the first in a view but not the second, so it has some strange limitations under some circumstances.
I have three tables, which are each 1:n. An entry in table1 has n entries in table2, and so on. Let's call them cars, wheels, and screws for illustration.
Screws can be clean(1) or rusty(2). I am joining them together, because I want to count two things. First, I want to have rows telling me how many good/bad screws per wheel I have for each car. So basically I am getting:
car_id wheel_id screw_state count(screws)
1 1 1 3
1 1 2 7
1 2 1 5
1 2 2 3
2 1 1 1
... and so on...
Now I want a second fact, namely how many rusty and clean screws I have for all wheels per car, without needing to know each specific number per wheel.
So basically now I just leave off the GROUP BY over wheel_id, like this:
car_id screw_state count(screws)
1 1 8
1 2 10
2 1 1
... and so on...
The thing is, I would need both of them in one single query, because else I'd have a lot of sorting and rearranging to do.
I believe the second, easier count over the total screws per car should be done as a subquery, but can I join the first, bigger query easily with a subquery?
How is this done?
I would be happy over a quite specific answers, because I am not really an SQL wizard.
edit : I am working on an ORM, so funky thinks like below (hacking the col values to some constant) can't be done there easily. I have to get this solution working there, so JOIN/subquery/UNIONs without funky workarounds would be great.
SELECT car_id, wheel_id, screw_state, count(screws)
FROM cars C, wheels W, screws S
WHERE W.car_id = C.car_id
AND S.wheel_id = W.wheel_id
GROUP BY car_id, wheel_id, screw_state
UNION ALL
SELECT car_id, -1 AS wheel_id, screw_state, count(screws)
FROM cars C, wheels W, screws S
WHERE W.car_id = C.car_id
AND S.wheel_id = W.wheel_id
GROUP BY car_id, screw_state
ORDER BY car_id
you can UNION 2 queries, the second one for all wheels per car, that's why wheel_id = -1.
result:
car_id wheel_id screw_state count(screws)
1 1 1 3
1 1 2 7
1 2 1 5
1 2 2 3
1 -1 1 8
1 -1 2 10
2 1 1 1
2 -1 1 1
...
A quick search says that MySQL supports GROUPING SETS. This is a good candidate for that feature:
SELECT car_id, wheel_id, screw_state, count(screws)
FROM cars C
JOIN wheels W ON W.car_id = C.car_id
JOIN screws S ON S.wheel_id = W.wheel_id
GROUP BY GROUPING SETS (
(car_id, screw_state, wheel_id),
(car_id, screw_state)
)
ORDER BY car_id, wheel_id, screw_state