In SQL, how to select all rows that satisfy multiple AND conditions (not OR) of the same column?
Such as: "select all users who speak these 3 languages (language_id == 1 AND language_id == 2 AND language_id ==3)" where language_id is a column
id | user_id | language_id
--------------------------
1 | 1 | 1
2 | 2 | 1
3 | 2 | 2
4 | 3 | 1
5 | 4 | 1 << which users speak this language )
6 | 4 | 2 << AND speak this language ) => expected result: user_id == 4
7 | 4 | 3 << AND speak this language )
8 | 5 | 1
9 | 6 | 1
10 | 7 | 1
First select all users having the wanted languages, count the languages and then restrict the users to have the language count equal to the count of the wanted languages.
SELECT user_id
FROM (SELECT used_id,COUNT(*)
FROM [table_name]
WHERE language_id IN (1,2,3)
GROUP BY user_id
HAVING COUNT(*)=3
) i;
You have some ways to do that.
One simple way would be to create a view returning the user_id with the count for each language, for example:
CREATE VIEW myView
AS
SELECT DISTINCT T0.user_id
,(SELECT COUNT(*) FROM [myTable] WHERE user_id=T0.user_id AND language_id=1) AS L1
,(SELECT COUNT(*) FROM [myTable] WHERE user_id=T0.user_id AND language_id=2) AS L2
,(SELECT COUNT(*) FROM [myTable] WHERE user_id=T0.user_id AND language_id=3) AS L3
FROM [myTable] AS T0
GO
You should get a result like this:
Then, you only need to query this view, getting just the user_id where L1>0 AND L2>0 AND L3>0...
SELECT * FROM myView WHERE L1>0 AND L2>0 AND L3>0
Regards,
Related
My task is to find all those subjects, by their id, that have (at least one, but) the fewest lowest passing grades in the database (the grade being the grade 6). I've managed to write the solution with three queries, however my task is to write it as a single query in MySQL. Thank you in advance.
-- 1. single query "solution"
SELECT subject_id FROM (SELECT subject_id, COUNT(*) AS six_count
FROM exams WHERE grade = 6
GROUP BY subject_id) AS sixes
WHERE subject_id = (SELECT MIN(six_count) FROM sixes);
-- 2. multiple queries solution
CREATE TABLE sixes AS (SELECT subject_id, COUNT(*) AS six_count
FROM exams WHERE grade = 6
GROUP BY subject_id);
SELECT subject_id FROM sixes
WHERE subject_id = (SELECT MIN(six_count) FROM sixes);
DROP TABLE sixes;
EDIT:
Exams table example:
| subject_id | student_id | exam_year | exam_mark | grade | exam_date |
| 1 | 20100022| 2011 | 'apr' | 10 | 2011-04-11 |
| 2 | 20100055| 2011 | 'oct' | 6 | 2011-10-04 |
| 3 | 20110030| 2011 | 'jan1' | 7 | 2011-01-26 |
| 5 | 20110055| 2011 | 'jan2' | 6 | 2011-02-13 |
| 5 | 20110001| 2011 | 'jun1' | 8 | 2011-06-23 |
This should do the trick. The sub query selects the first lowest number of sixes. The main query selects all subjects with that number. The trick is in ORDER BY count(*) LIMIT 1, which makes the sub query return the record with the lowest count.
SELECT
subject_id,
count(*) as six_count
FROM exams
WHERE grade = 6
GROUP BY subject_id
HAVING count(*) =
( SELECT count(*)
FROM exams
WHERE grade = 6
GROUP BY subject_id
ORDER BY count(*)
LIMIT 1
)
This pattern should do the trick. Generalized names.
SELECT subjectID
FROM TEST_DATA
WHERE grade = 6
GROUP
BY SubjectID
HAVING COUNT(1) =
( SELECT count(1) AS minCount
FROM TEST_DATA
WHERE grade = 6
GROUP
BY subjectID
ORDER
BY minCount
LIMIT 1
);
Im trying to get the most recent row of a table
user_quiz:
+--------+-----------+-------------+-------------------+------------+
|quiz_id |userid | module_id |number_of_questions| user_score |
+--------+-----------+-------------+-------------------+-------- ---+
| 1 | 1 | 1 | 5 | 5 |
| 2 | 2 | 2 | 10 | 9 |
| 3 | 1 | 1 | 10 | 9 |
+--------+-----------+-------------+-------------------+------------+
I have used the query:
SELECT * FROM user_quiz WHERE userid = 1 ORDER BY quiz_id DESC LIMIT 1
which correctly retrieves the last row.
However I want to link the module_id with another table:
module:
+---------+------------+
|module_id|module_name |
+---------+------------+
| 1 | Forces |
| 2 | Electricity|
+---------+------------+
And retrieve the module name.
The result of the query will be used to print out the users most recent quiz:
Most recent quiz: Forces - Number of questions: 10 - User Score: 9
Is this possible using just one query?
You just need a JOIN:
SELECT uq.*, m.module_name
FROM user_quiz uq JOIN
modules m
ON uq.module_id = m.module_id
WHERE uq.userid = 1
ORDER BY uq.quiz_id DESC
LIMIT 1;
A more simple query to achieve the same would be
SELECT
user_quiz.quiz_id,
user_quiz.number_of_questions,
user_quiz.user_score,
modules .module_name
FROM user_quiz JOIN modules
ON user_quiz.module_id = modules.module_id
WHERE user_quiz.userid = 1
ORDER BY user_quiz.quiz_id DESC
LIMIT 1
If you want to get the same results for all the users, you could use a bit more sophisticated query
SELECT
user_quiz_virtual_table.userid,
user_quiz_virtual_table.quiz_id,
user_quiz_virtual_table.number_of_questions,
user_quiz_virtual_table.user_score,
modules.module_name
FROM (
SELECT
user_quiz.userid
user_quiz.quiz_id,
user_quiz.module_id
user_quiz.number_of_questions,
user_quiz.user_score
FROM user_quiz
ORDER BY user_quiz.quiz_id DESC
GROUP BY userid
) AS user_quiz_virtual_table
JOIN modules ON user_quiz_virtual_table.module_id = modules.module_id
I am in a very complicated problem. Let me explain you first what I am doing right now:
I have a table name feedback in which I am storing grades against course id. The table looks like this:
+-------+-------+-------+-------+-----------+--------------
| id | cid | grade |g_point| workload | easiness
+-------+-------+-------+-------+-----------+--------------
| 1 | 10 | A+ | 1 | 5 | 4
| 2 | 10 | A+ | 1 | 2 | 4
| 3 | 10 | B | 3 | 3 | 3
| 4 | 11 | B+ | 2 | 2 | 3
| 5 | 11 | A+ | 1 | 5 | 4
| 6 | 12 | B | 3 | 3 | 3
| 7 | 11 | B+ | 2 | 7 | 8
| 8 | 11 | A+ | 1 | 1 | 2
g_point has just specific values for the grades, thus I can use these values to show the user courses sorted by grades.
Okay, now first my task is to print out the grade of each course. The grade can be calculated by the maximum occurrence against each course. For example from this table we can see the result of cid = 10 will be A+, because it is present two times there. This is simple. I have already implemented this query which I will write here in the end.
The main problem is when we talk about the course cid = 11 which has two different grades. Now in that situation client asks me to take the average of workload and easiness of both these courses and whichever course has the greater average should be shown. The average would be computed like this:
all workload values of the grade against course
+ all easiness values of the grade against course
/ 2
From this example cid = 11 has four entries,have equal number of grades against a course
B+ grade average
avgworkload(2 + 7)/2=x
avgeasiness(3 + 8)/2 = y
answer x+y/2 = 10
A+ grade average
avgworkload(5 + 1)/2=x
avgeasiness(4 + 2)/2 = y
answer x+y/2 = 3
so the grade should be B+.
This is the query which I am running to get the max occurrence grade
SELECT
f3.coursecodeID cid,
f3.grade_point p,
f3.grade g
FROM (
SELECT
coursecodeID,
MAX(mode_qty) mode_qty
FROM (
SELECT
coursecodeID,
COUNT(grade_point) mode_qty
FROM feedback
GROUP BY
coursecodeID, grade_point
) f1
GROUP BY coursecodeID
) f2
INNER JOIN (
SELECT
coursecodeID,
grade_point,
grade,
COUNT(grade_point) mode_qty
FROM feedback
GROUP BY
coursecodeID, grade_point
) f3
ON
f2.coursecodeID = f3.coursecodeID AND
f2.mode_qty = f3.mode_qty
GROUP BY f3.coursecodeID
ORDER BY f3.grade_point
Here is SQL Fiddle.
I added a table Courses with the list of all course IDs, to make the main idea of the query easier to see. Most likely you have it in the real database. If not, you can generate it on the fly from feedback by grouping by cid.
For each cid we need to find the grade. Group feedback by cid, grade to get a list of all grades for the cid. We need to pick only one grade for a cid, so we use LIMIT 1. To determine which grade to pick we order them. First, by occurrence - simple COUNT. Second, by the average score. Finally, if there are several grades than have same occurrence and same average score, then pick the grade with the smallest g_point. You can adjust the rules by tweaking the ORDER BY clause.
SELECT
courses.cid
,(
SELECT feedback.grade
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS CourseGrade
FROM courses
ORDER BY courses.cid
result set
cid CourseGrade
10 A+
11 B+
12 B
UPDATE
MySQL doesn't have lateral joins, so one possible way to get the second column g_point is to repeat the correlated sub-query. SQL Fiddle
SELECT
courses.cid
,(
SELECT feedback.grade
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS CourseGrade
,(
SELECT feedback.g_point
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS CourseGPoint
FROM courses
ORDER BY CourseGPoint
result set
cid CourseGrade CourseGPoint
10 A+ 1
11 B+ 2
12 B 3
Update 2 Added average score into ORDER BY SQL Fiddle
SELECT
courses.cid
,(
SELECT feedback.grade
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS CourseGrade
,(
SELECT feedback.g_point
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS CourseGPoint
,(
SELECT (AVG(workload) + AVG(easiness))/2
FROM feedback
WHERE feedback.cid = courses.cid
GROUP BY
cid
,grade
ORDER BY
COUNT(*) DESC
,(AVG(workload) + AVG(easiness))/2 DESC
,g_point
LIMIT 1
) AS AvgScore
FROM courses
ORDER BY CourseGPoint, AvgScore DESC
result
cid CourseGrade CourseGPoint AvgScore
10 A+ 1 3.75
11 B+ 2 5
12 B 3 3
If I understood well you need an inner select to find the average, and a second outer select to find the maximum values of the average
select cid, grade, max(average)/2 from (
select cid, grade, avg(workload + easiness) as average
from feedback
group by cid, grade
) x group by cid, grade
This solution has been tested on your data usign sql fiddle at this link
If you change the previous query to
select cid, max(average)/2 from (
select cid, grade, avg(workload + easiness) as average
from feedback
group by cid, grade
) x group by cid
You will find the max average for each cid.
As mentioned in the comments you have to choose wich strategy use if you have more grades that meets the max average. For example if you have
+-------+-------+-------+-------+-----------+--------------
| id | cid | grade |g_point| workload | easiness
+-------+-------+-------+-------+-----------+--------------
| 1 | 10 | A+ | 1 | 5 | 4
| 2 | 10 | A+ | 1 | 2 | 4
| 3 | 10 | B | 3 | 3 | 3
| 4 | 11 | B+ | 2 | 2 | 3
| 5 | 11 | A+ | 1 | 5 | 4
| 9 | 11 | C | 1 | 3 | 6
You will have grades A+ and C soddisfing the maximum average 4.5
So my current table looks like this :
| UserID | QuestionID | GameID |
| 1 | 30 | 2 |
| 1 | 30 | 3 |
| 2 | 30 | 4 |
| 3 | 30 | 2 |
| 4 | 30 | 3 |
How would I return all the rows where the same UserID has a value for GameID 1, 2, 3 and 4? Basically trying to return all the users who have played Game 1, 2, 3 and 4
Assuming no duplicates of game id..
Select userID
from table
where gameID in (1,2,3,4)
group by UserID
having count(GameID) = 4
If I get the answer correct, it might be:
SELECT p.* FROM poll AS p WHERE p.UserID = <your_user_id> AND p.GameID IN (1,2,3,4)
or you are seeking for:
SELECT p.*, GROUP_CONCAT(p.GameID) FROM poll AS p WHERE p.UserID = <user_id> GROUP BY p.GameID
Assuming the tables are normalized and joined properly, simply use a WHERE clause:
WHERE colname = value1 OR colname = value2 ...
or use the In operator
WHERE colname = In (value,value...)
http://beginner-sql-tutorial.com/sql-logical-operators.htm
SELECT
UserID
FROM (
SELECT
UserID,
GROUP_CONCAT(GameID ORDER BY GameID) as Games
FROM some_table
GROUP BY UserID
) AS baseview
WHERE Games="1,2,3,4"
Please understand, this is a performance killer - it creates the GROUP_CONCAT for all users.
Let's say we have this query
SELECT * FROM table
And this result from it.
id | user_id
------------
1 | 1
------------
2 | 1
------------
3 | 2
------------
4 | 1
How could I get the count of how often a user_id appears as another field (without some major SQL query)
id | user_id | count
--------------------
1 | 1 | 3
--------------------
2 | 1 | 3
--------------------
3 | 2 | 1
--------------------
4 | 1 | 3
We have this value currently in code, but we are implementing sorting to this table and I would like to be able to sort in the SQL query.
BTW if this is not possible without some major trick, we are just going to skip sorting on that field.
You'll just want to add a subquery on the end, I believe:
SELECT
t.id,
t.user_id,
(SELECT COUNT(*) FROM table WHERE user_id = t.user_id) AS `count`
FROM table t;
SELECT o.id, o.user_id, (
SELECT COUNT(id)
FROM table i
WHERE i.user_id = o.user_id
GROUP BY i.user_id
) AS `count`
FROM table o
I suspect this query as not being a performance monster but it should work.