I have this table:
+--------+------+----------+
| fromId | toId | messages |
+--------+------+----------+
| 10 | 2 | 'text' |
| 10 | 4 | 'text' |
| 4 | 10 | 'text' |
| 5 | 10 | 'text' |
| 5 | 10 | 'text' |
| 10 | 3 | 'text' |
| 6 | 10 | 'text' |
+--------+------+----------+
Every row is a message from fromId to toId.
As you can see I have 5 conversations in which user whose ID is 10 is involved:
10 with 2
10 with 4
10 with 5
10 with 3
10 with 6
How can I count them in a Select query??
I have tried this one:
SELECT * FROM messaggi WHERE fromId = 10 OR toID = 10 GROUP BY (fromId)
but something tells me that I have to try a SELECT from another SELECT, I think it's called a subquery.
The answer is equal to the number of rows returned by this query:
SELECT DISTINCT from_id x FROM my_table WHERE to_id = 10
UNION
SELECT DISTINCT to_id x FROM my_table WHERE from_id = 10;
If I understand 10, 5 is the same as 5, 10 so doesnt matter who start the conversation, so:
SQL DEMO
SELECT COUNT(*)
FROM (SELECT DISTINCT
LEAST(`fromId`, `toId`) AS a,
GREATEST(`fromId`, `toId`) AS b
FROM Table1
WHERE 10 in (`fromId`, `toId`)
) T
So we need to find the total number of distinct conversations in any direction. What we can do is query the results and union them together but switch the columns around for one of the queries. This gives us all results for conversations in any direction. We then can count the distinct results to find out how many conversations there are for an individual.
SELECT COUNT(DISTINCT *) FROM
(SELECT fromId as col1, toId as col2 FROM conversations WHERE fromId = 10
UNION
SELECT toId as col1, fromId as col2 FROM conversations WHERE toId = 10)
I would suggest you to change the way it is constructed. Have one table for threads:
TID
---
1
2
3
4
5
6
7
And now, each thread can have any (right now 2) number of participants. So, let's have participants table.
TID | UID
----+----
1 | 10
1 | 2
2 | 10
2 | 4
3 | 4
3 | 10
4 | 5
4 | 10
5 | 5
5 | 10
6 | 10
6 | 3
7 | 6
7 | 10
Now, if you find the count of the participated ones, in a distinct way:
SELECT DISTINCT(GROUP_CONCAT(`UID` ORDER BY `UID` ASC)) FROM participants GROUP BY `TID`
You get this:
And finally, wrapping it with COUNT gives you 5:
SELECT COUNT(*) FROM (SELECT DISTINCT(GROUP_CONCAT(`UID` ORDER BY `UID` ASC)) FROM `participants` GROUP BY `TID`) AS T
Related
Today I have posted a question and got a good answer: Stuck in building mysql query.
I though it helped me, but I've discovered that it returns wrong data. So I'm reposting the question here, with an answer I received, as well I will explain the problem why it is not working for me.
Example of data:
id | item_id | user_id | bid_price
----------------------------------
1 | 1 | 11 | 1
2 | 1 | 12 | 2
3 | 1 | 13 | 3
4 | 1 | 14 | 1
5 | 1 | 15 | 4
6 | 2 | 16 | 2
7 | 2 | 17 | 1
8 | 3 | 18 | 2
9 | 3 | 19 | 3
10 | 3 | 18 | 2
Expected result:
id | item_id | user_id | bid_price
----------------------------------
1 | 1 | 11 | 1
7 | 2 | 17 | 1
8 | 3 | 18 | 2
Offered solution:
select m.id, m.item_id, m.user_id, m.bid_price
from my_table m
inner join (
select item_id, min(id) min_id, min(bid_price) min_price
from my_table
where item_id IN (1,2,3)
group by item_id
) t on t.item_id = m.item_id
and t.min_price= m.bid_price
and t.min_id = m.id
The problem:
In the sub query the minimum ID is selected entire the group by (item_id) statement and doesn't reflects according to minimum bid_price.
In other words, the minimum id is selected not depending on the price field at all. So, in the result I will get minimum price and minimum id of the group, but this will not be the same row! The id can be related to the row with another bet_price value.
How this query can be adjusted? Thank you in advance!
SELECT min(m.id) AS id, m.item_id, m.user_id, m.bid_price
FROM my_table m
INNER JOIN (
SELECT item_id, min(bid_price) AS min_price
FROM my_table
GROUP BY item_id
) t ON t.item_id = m.item_id
AND t.min_price= m.bid_price
GROUP BY item_id
Output
id item_id user_id bid_price
1 1 11 1
7 2 17 1
8 3 18 2
Live Demo
http://sqlfiddle.com/#!9/a52dc6/13
SELECT DISTINCT
t1.item_id,
t1.bid_price
FROM tab1 t1
WHERE NOT exists(SELECT 1
FROM tab1 t2
WHERE t2.item_id = t1.item_id
AND t2.bid_price < t1.bid_price)
AND t1.item_id IN (1, 2, 3);
http://sqlfiddle.com/#!9/615e0a/5
I have a SQL table user_game which contains the games that a user owns:
| id | user_id | game_id |
|----|---------|---------|
| 83 | 1 | 1 |
| 84 | 1 | 2 |
| 85 | 1 | 3 |
| 86 | 2 | 2 |
| 87 | 2 | 3 |
| 88 | 2 | 4 |
| 89 | 3 | 2 |
I am trying to count the number of users which have 1 game, 2 games, 3 games.. etc.
User 1 has 3 games, User 2 has 3 games, and User 3 has 1 game. Therefore these are the results I want to achieve:
| no_of_games | COUNT(no_of_games) |
|-------------|--------------------|
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
COUNT(no_of_games) is the number of users that have that number of games.
I can individually get the number of users for each no_of_games with this query:
-- Select no. of users with 1 game
SELECT no_of_games, COUNT(no_of_games)
FROM
(
-- Select no. of games each user has
SELECT user_id, COUNT(1) as no_of_games
FROM user_game
GROUP BY user_id
) as A
WHERE no_of_games = 1;
which gives the results:
| no_of_games | COUNT(no_of_games) |
|-------------|--------------------|
| 1 | 1 |
However I have to change the no_of_games = 1 to 2, 3, 4... manually and UNION them with this solution and I can't do it for ~60 cases.
Is there a simpler way to achieve this?
Your problem is a bit tricky, because groups of games which do not appear in your data with a certain frequency (e.g. 2) will not appear in the result set just using your original table. In the query below, I use a second table called nums which simply contains the sequence 1 through 10 representing counts of number of games. By using a LEFT JOIN we can retain each game count in the final result set.
SELECT t1.no_of_games,
COALESCE(t2.no_of_games_count, 0) AS no_of_games_count
FROM nums t1
LEFT JOIN
(
SELECT t.no_of_games, COUNT(*) AS no_of_games_count
FROM
(
SELECT COUNT(*) AS no_of_games
FROM user_game
GROUP BY user_id
) t
GROUP BY t.no_of_games
) t2
ON t1.no_of_games = t2.no_of_games
ORDER BY t1.no_of_games
And here is the definition I used for nums:
CREATE TABLE nums (`no_of_games` int);
INSERT INTO nums (`no_of_games`)
VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
Demo here:
SQLFiddle
You can find count of games for each user and then find count of users for each count of games.
select cnt no_of_games, count(*) cnt_no_of_games
from(
select user_id, count(*) cnt
from your_table
group by user_id
) t group by cnt;
I have a table of hits for various users:
HITS:
id | userid
1 | 1
2 | 1
3 | 2
4 | 1
5 | 2
6 | 2
I want the fastest possible way to get a list of these items ranked by ID. So this:
HITS RANKED:
id | userid | ranks
1 | 1 | 1
2 | 1 | 2
3 | 2 | 1
4 | 1 | 3
5 | 2 | 2
6 | 2 | 3
I want to avoid joining two tables to each other, as this takes forever when the tables get big. Any other suggestions?
SELECT ID,
UserID,
Ranks
FROM
(
SELECT id,
userid,
#group:=CASE WHEN #temp <> userid THEN 1 ELSE #group+1 END AS ranks,
#temp:=userid AS clset
FROM (SELECT #group:= 0) s,
(SELECT #temp:= 0) c,
(SELECT * FROM hits ORDER BY userid, id) t
) x
ORDER BY ID
SQLFiddle Demo
i have a scenario, lets say 3 users review a business of id 10, how can i get all the unique id of the user who review that business and and use that unique id to find another business review which is not equal to 10 ?
sample table user_review:
review_id | user_id | business_id | rating | review_date
1 2 10 3 20121030124001
2 2 9 3 20121022120627
3 2 10 4 20121023120627
4 3 10 4 20121024120627
5 3 6 3 20121022140627
6 4 10 2 20121025120627
7 4 10 5 20121030120627
8 3 10 2 20121010120627
9 4 8 5 20121028120627
i should get result of these
review_id | user_id | business_id | rating | review_date
2 2 9 3 20121022120627
5 3 6 3 20121022140627
9 4 8 5 20121028120627
In a above result if there is 2 reviews for a same user_id and same business_id the latest one should be return.Thanks
Try this query:
Here is link to sqlfidle with running results http://sqlfiddle.com/#!2/cd4ea/1
SELECT
tblreview.*,tblusers.user_name
FROM
(
SELECT
MAX(tblreview.review_id) review_id
, tblreview.user_id
FROM
(
SELECT
DISTINCT user_id
FROM
tblreview
WHERE business_id = 10
) reviewsb10
INNER JOIN
tblreview
ON
tblreview.user_id = reviewsb10.user_id
AND
tblreview.business_id <> 10
GROUP BY
user_id
) tblLastReviewPerUser
INNER JOIN
tblreview
ON
tblreview.review_id = tblLastReviewPerUser.review_id
INNER JOIN
tblusers
ON
tblusers.user_id = tblLastReviewPerUser.user_id
SELECT t1.*
FROM TableName t1
INNER JOIN
(
SELECT user_id, business_id, MAX(review_date) review_date
FROM TableName
WHERE business_id <> 10
GROUP BY user_id, business_id
) t2 ON t1.user_id = t2.user_id
AND t1.review_date = t2.review_date
AND t1.business_id = t2.business_id
Try this query -
SELECT * FROM (
SELECT * FROM user_review
ORDER BY IF(business_id = 10, 1, 0), review_date DESC
) t
GROUP BY user_id
HAVING
COUNT(IF(business_id = 10, 1, NULL)) > 0
AND COUNT(IF(business_id <> 10, 1, NULL)) > 0
+-----------+---------+-------------+--------+----------------+
| review_id | user_id | business_id | rating | review_date |
+-----------+---------+-------------+--------+----------------+
| 2 | 2 | 9 | 3 | 20121022120627 |
| 5 | 3 | 6 | 3 | 20121022140627 |
| 9 | 4 | 8 | 5 | 20121028120627 |
+-----------+---------+-------------+--------+----------------+
I have the next example table:
id | user_id | data
-------------------
1 | 1 | 10
2 | 2 | 10
3 | 2 | 10
4 | 1 | 10
5 | 3 | 10
6 | 4 | 10
7 | 4 | 10
8 | 5 | 10
9 | 5 | 10
10 | 2 | 10
11 | 6 | 10
12 | 3 | 10
13 | 1 | 10
I need to create a SELECT query, that LIMITS my data. For example, I have a limit range (1, 3) (page number = 1, row count = 3). It should selects rows with first 3 unique user_id. And if there are some rows in the end of table with this first user_id's, they should be included to the result. LIMIT statement is bad for this query, because I can get more than 3 rows. Output for my limit should be:
id | user_id | data
-------------------
1 | 1 | 10
2 | 2 | 10
3 | 2 | 10
4 | 1 | 10
5 | 3 | 10
10 | 2 | 10
12 | 3 | 10
13 | 1 | 10
Can you help me to generate this query?
How about:
SELECT *
FROM table
WHERE user_id IN
(SELECT distinct(user_id) FROM table order by user_id LIMIT 3);
What about something like this?
SELECT * FROM table WHERE user_id BETWEEN (number) AND (number+row count)
I know it isn't working but you should be able to make it work ^^
The sample code below can be used for Oracle & Mysql. (use TOP for SQL Server & Sybase)
You get all the results from your table (t1) that match the top 3 user_id (t2) (check the MySQL manual for the limit function)
SELECT *
FROM exampletable t1
INNER JOIN (
SELECT DISTINCT user_id
FROM exampletable
ORDER BY user_id
LIMIT 0,3 -- this is the important part
) AS t2 ON t1.user_id = t2.user_id
ORDER BY id
For the next 3 id's change the limit 0,3 to limit 3,6.