I have two tables which join themselves by a field called user_id. The first table called sessions can have multiple lines for the same day. I'm trying to find a way of selecting the total of that sessions without repeating the days (sort of).
Example:
Table sessions
ID | user_id | datestart
1 1 2014-08-05
2 1 2014-08-05
3 2 2014-08-05
As you can see there are two lines that are repeated (the first and second). If I query SELECT COUNT(sess.id) AS total this will retrieve 3, but I want it to retrieve 2 because the first two lines have the same user_id so it must count as one.
Using the clause Group By will retrieve two different lines: 2 and 1, which is also incorrect.
You can view a full example working at SQLFiddle.
Is there anyway of solving this only by query or do I need to do it by language?
I think you are looking for count(distinct):
SELECT COUNT(distinct user_id) AS total
FROM sessions sess INNER JOIN
users user
ON user.id = sess.user_id
WHERE user.equipment_id = 1 AND
sess.datestart = CURDATE();
If I understand the problem correctly, you want the number of users with sessions, rather than number of unique sessions. Use DISTINCT:
SELECT COUNT(DISTINCT(user_id)) FROM sessions,users WHERE user_id=users.id
Try this way:
SELECT COUNT(distinct sess.user_id) AS total
FROM sessions AS sess
INNER JOIN users AS user ON user.id = sess.user_id
WHERE user.equipment_id = 1 AND sess.datestart = CURDATE()
Sql Fiddle
Related
I tried to write a query, but unfortunately I didn't succeed.
I want to know how many packages delivered over a given period by a person.
So I want to know how many packages were delivered by John (user_id = 1) between 01-02-18 and 28-02-18. John drives another car (another plate_id) every day.
(orders_drivers.user_id, plates.plate_name, orders.delivery_date, orders.package_amount)
I have 3 table:
orders with plate_id delivery_date package_amount
plates with plate_id plate_name
orders_drivers with plate_id plate_date user_id
I tried some solutions but didn't get the expected result. Thanks!
Try using JOINS as shown below:
SELECT SUM(o.package_amount)
FROM orders o INNER JOIN orders_drivers od
ON o.plate_id=od.plate_id
WHERE od.user_id=<the_user_id>;
See MySQL Join Made Easy for insight.
You can also use a subquery:
SELECT SUM(o.package_amount)
FROM orders o
WHERE EXISTS (SELECT 1
FROM orders_drivers od
WHERE user_id=<user_id> AND o.plate_id=od.plate_id);
SELECT sum(orders.package_amount) AS amount
FROM orders
LEFT JOIN plates ON orders.plate_id = orders_drivers.plate_id
LEFT JOIN orders_driver ON orders.plate_id = orders_drivers.plate_id
WHERE orders.delivery_date > date1 AND orders.delivery_date < date2 AND orders_driver.user_id = userid
GROUP BY orders_drivers.user_id
But seriously, you need to ask questions that makes more sense.
sum is a function to add all values that has been grouped by GROUP BY.
LEFT JOIN connects all tables by id = id. Any other join can do this in this case, as all ids are unique (at least I hope).
WHERE, where you give the dates and user.
And GROUP BY userid, so if there are more records of the same id, they are returned as one (and summed by their pack amount.)
With the AS, your result is returned under the name 'amount',
If you want the total of packageamount by user in a period, you can use this query:
UPDATE: add a where clause on user_id, to retrieve John related data
SELECT od.user_id
, p.plate_name
, SUM(o.package_amount) AS TotalPackageAmount
FROM orders_drivers od
JOIN plates p
ON o.plate_id = od.plate_id
JOIN orders o
ON o.plate_id = od.plate_id
WHERE o.delivery_date BETWEEN convert(datetime,01/02/2018,103) AND convert(datetime,28/02/2018,103)
AND od.user_id = 1
GROUP BY od.user_id
, p.plate_name
It groups rows on user_id and plate_name, filter a period of delivery_date(s) and then calculate the sum of packageamount for the group
My SQL's more than a little rusty, and I'm having trouble getting this to work, so any assistance would be greatly appreciated.
I've got three tables:
sessions
---------------
id
session_visits
---------------
id | session_id
searches
---------------
id | session_visit_id
And I want to get a list of all sessions with the total visits and searches for each sessions, which is linked by the session_visits table. I can get the visits fine, but am having trouble getting the total of searches for each session too.
So far I've got
SELECT *,(SELECT Count(*)
FROM session_visits
WHERE session_id = sessions.id) AS num_visits,
(SELECT Count(*)
FROM searches
WHERE session_visit_id = (SELECT * FROM session_visits
WHERE session_id = sessions.id)) AS total_searches
FROM sessions
Which is failing on every count! Am I going about this the right way or am I fundamentally doing it wrong?
You can do this in one query, by joining the 3 tables together, and then use aggregates COUNT DISTINCT (to eliminate duplicated) and COUNT to get the total number of rows for the child and grandchild rows respectively, grouped by the Sessionid.
SELECT s.id AS SessionId, COUNT(DISTINCT sv.id) AS SessionVisits, COUNT(sr.ID) AS Searches
FROM sessions s
LEFT JOIN session_visits sv
ON s.id = sv.session_id
LEFT JOIN searches sr
ON sr.session_visit_id = sv.id
GROUP BY s.id;
SqlFiddle here
(Edit : Changed to left outer joins to handle scenarios where there are no visits for session, or no searches per visit)
query generates error because of column name is not mentioned in query
Operand should contain 1 column
and try with IN
I currently have 2 tables:
Favorite:
userID
drinkName
History:
userID
drinkName
I want to get the sum of the total times a specific userID shows up in each table, and then then the total number of times userID shows up in both tables.
(SELECT COUNT(userID) AS totalDrinks FROM History
WHERE userID = 'sai') union
(SELECT COUNT(userID) AS totalDrinks FROM Favorite
WHERE userID = 'sai')
So that code gets me the following output:
totalDrinks
4
2
However I am trying to use the MySQL sum function and that's not adding the two things up though.
So I was wondering how I would rewrite my query to output 6?
SELECT SUM(userID)as totalDrinks FROM History h
JOIN Favorite f ON h.userID=f.userID
GROUP BY userID
WHERE userID = 'sai'
Your UNION approach was almost there. You will have to SUM the result of both queries:
SELECT SUM(totalDrings) totalDrings FROM (
SELECT COUNT(*) totalDrinks FROM History
WHERE userID = 'sai'
UNION ALL
SELECT COUNT(*) FROM Favorite
WHERE userID = 'sai'
) s
A few things to note. You should use UNION ALL otherwise if the COUNTs result in the same number then they will be added only once. Another thing is that you should not use an INNER JOIN in here as that will force the users to be present in both tables.
I have 4 queries I need to excecute in order to suggest items to users based on items they've already expressed an interest in:
Select 5 random items the user already likes
SELECT item_id
FROM user_items
WHERE user_id = :user_person
ORDER BY RAND()
LIMIT 5
Select 50 people who like the same items
SELECT user_id
FROM user_items
WHERE user_id != :user_person
AND item_id = :selected_item_list
LIMIT 50
SELECT all items that the original user likes
SELECT item_id
FROM user_items
WHERE user_id = :user_person
SELECT 5 items the user doesn't already like to suggest to the user
SELECT item_id
FROM user_items
WHERE user_id = :user_id_list
AND item_id != :item_id_list
LIMIT 5
What I would like to know is how would I excecute this as one query?
There are a few reasons for me wanting to do this:
at the moment, I have to excecute the 'select 50 people' query 5 times and pick the top 50 people from it
I then have to excecute the 'select 5 items' query 50 * (number of items initial user likes)
Once the query has been excecuted, I intend to store the query result in a cookie (if the user gives consent to me using cookies, otherwise they don't get the 'item suggestion' at all) with the key being a hash of the query, meaning it will only fire once a day / once a week (that's why I return 5 suggestions and select a key at random to display)
Basically, if anybody knows how to write these queries as one query, could you show me and explain what is going on in the query?
This will select all items you need:
SELECT DISTINCT ui_items.item_id
FROM user_items AS ui_own
JOIN user_items AS ui_others ON ui_own.item_id = ui_others.item_id
JOIN user_items AS ui_items ON ui_others.user_id = ui_items.user_id
WHERE ui_own.user_id = :user_person
AND ui_others.user_id <> :user_person
AND ui_items.item_id <> ui_own.item_id
(please, check if result are exact same with you version - I tested it on a very small fake data set)
Next you just cache this list and show 5 items randomly, because ORDER BY RAND() is VERY inefficient (non-deterministic query => no caching)
EDIT: Added the DISTINCT to not show duplicate rows.
You can also return a most popular suggestions in descending popularity order by removing DISTINCT and adding the following code to the end of the query:
GROUP BY ui_items.item_id
ORDER BY COUNT(*) DESC
LIMIT 20
To the end of the query which will return the 20 most popular items.
I have a query which works when I use DISTINCT. However I have a feeling I could rewrite the query in a way that would help me avoid use of DISTINCT, which would make easier(quicker) for the database to process the query.
If there is no point in rewriting the query, please explain, if there is, please look at simplified query and give me a hint how to reformulate it so I wouldn't get duplicates in the first place.
SELECT Us.user_id, COUNT( DISTINCT Or.order_id ) AS orders
FROM users AS Us
LEFT JOIN events AS Ev ON Ev.user_id = Us.user_id
LEFT JOIN orders AS Or ON Or.event_id = Ev.event_id
OR Or.user_id = Us.user_id
GROUP BY Us.user_id
Short description of the query: I have a table of users, of their events and orders. Sometimes orders have column user_id, but mostly it is null and they have to be connected via event table.
Edit:
These are results of the simplified query I wrote, first without distinct and then including distinct.
user_id orders
3952 263
3953 7
3954 2
3955 6
3956 1
3957 0
...
user_id orders
3952 79
3953 7
3954 2
3955 6
3956 1
3957 0
...
Problem fixed:
SELECT COALESCE( Or.user_id, Ev.user_id ) AS user, COUNT( Or.order_id ) AS orders
FROM orders AS Or
LEFT JOIN events AS Ev ON Ev.event_id = Or.event_id
GROUP BY COALESCE( Or.user_id, Ev.user_id )
If an order can be associated with multiple events, or a user with an event multiple times, then it is possible for the same order to be associated with the same user multiple times. In this scenario, using DISTINCT will count that order only once per user whereas omitting it will count that order once for each association with the user.
If you're after the former, then your existing query is your best option.
You are not getting anything from the user table, nor the events table, so why join them. Your last "OR" clause makes explicit reference that it has a user_ID column. I would hope your order table has an index on the user ID placing the order, then you could just do
select
user_id,
count(*) as Orders
from
orders
group by
user_id