I have a table:
+----------------+----------------+------------------+-------+
| Student_Id | Student_Name | Assessment_Type | Mark |
+----------------+----------------+------------------+-------+
| 300 | John | Assignment | 1 |
| 200 | Liz | Final | 2 |
| 300 | John | Mid-term | 3 |
| 100 | Sue | Mid-term | 4 |
| 200 | Liz | Project | 5 |
| 300 | John | Assignment | 6 |
| 200 | Liz | Final | 7 |
| 300 | John | Mid-term | 8 |
| 100 | Sue | Mid-term | 8 |
| 200 | Liz | Project | 9 |
+----------------+----------------+------------------+-------+
I would like to find the max mark grouped by Assessment_Type, and if there is a duplicate, show both, so in this case:
+----------------+----------------+------------------+-------+
| Student_Id | Student_Name | Assessment_Type | Mark |
+----------------+----------------+------------------+-------+
| 300 | John | Assignment | 6 |
| 200 | Liz | Final | 7 |
| 300 | John | Mid-term | 8 |
| 100 | Sue | Mid-term | 8 |
| 200 | Liz | Project | 9 |
+----------------+----------------+------------------+-------+
What I have only shows one of them:
SELECT Student_Id, Student_Name, Assessment_Type, max(mark) FROM STUDENT_ASSESSMENT group by Student_Id, Assessment_Type;
Edit: Added more details to question.
You can find max marks in each assessment type and then compare that max(marks) and assessment type with each row.
select * from STUDENTS_ASSESSMENT where (Assessment_Type,marks) in
((select Assessment_Type,max(marks) from STUDENTS_ASSESSMENT groupby Assessment_Type));
You could find maximum value of the Mark column, then select rows that Mark value is equal to this value:
SELECT
Student_Id, Student_Name, Assessment_Type, Mark
FROM
STUDENT_ASSESSMENT FullSet
JOIN
(SELECT MAX(Mark) AS Mark FROM STUDENT_ASSESSMENT) MaxMark
USING (Mark);
Related
I need to find the sum of credits from click_stats where source = 'reward' for all users who have claimed at least one of the 3 promo codes AND have the total clicks displayed.
Tables:
+---------------------------------------------+
| click_stats |
+----+---------+--------+--------+------------+
| ID | Credits | Userid | Source | Clicked |
+----+---------+--------+--------+------------+
| 1 | 10 | jon | reward | 1602216005 |
| 2 | 5 | bob | reward | 1602216504 |
| 3 | 5 | jon | reward | 1602216137 |
| 4 | 5 | bob | reward | 1602216138 |
| 5 | 10 | jon | reward | 1602216139 |
| 6 | 5 | jon | reward | 1602216140 |
| 7 | 10 | bob | reward | 1602216150 |
| 8 | 10 | jon | reward | 1602216150 |
| 9 | 10 | sue | reward | 1602216150 |
| 10 | 10 | sue | prize | 1602216150 |
+----+---------+--------+--------+------------+
+-----------------------+
| promo_used |
+----+--------+---------+
| id | userid | promoid |
+----+--------+---------+
| 1 | bob | 1 |
+----+--------+---------+
| 2 | bob | 2 |
+----+--------+---------+
| 3 | bob | 3 |
+----+--------+---------+
| 4 | jon | 1 |
+----+--------+---------+
| 5 | jon | 2 |
+----+--------+---------+
+------------------------+
| promo_codes |
+----+----------+--------+
| id | code | reward |
+----+----------+--------+
| 1 | forever1 | 20 |
+----+----------+--------+
| 2 | novgfy1 | 250 |
+----+----------+--------+
| 3 | novgfy2 | 500 |
+----+----------+--------+
My Query:
SELECT
click_stats.userid as Name,
sum(credits) as TotalClicks
FROM click_stats
JOIN promo_used
ON click_stats.userid = promo_used.userid
JOIN promo_codes
ON promo_used.promoid = promo_codes.id
WHERE
click_stats.source = 'reward'
and FROM_UNIXTIME(clicked) > '2020-10-08'
and (promo_codes.name like '%forever%'
or promo_codes.name like 'novgfy%')
group by
Name
having
TotalClicks > 10
Results when I run my query (returning the total number of clicks * number of promo codes used):
+--------------------+
| Results |
+------+-------------+
| Name | TotalClicks |
+------+-------------+
| bob | 60 |
+------+-------------+
| jon | 80 |
+------+-------------+
Results I am wanting (the total number of clicks only):
+--------------------+
| Expected Results |
+------+-------------+
| Name | TotalClicks |
+------+-------------+
| bob | 20 |
+------+-------------+
| jon | 40 |
+------+-------------+
The problem (I suspect) is that it is summing the click_stats every time it finds a match for promo_codes.name. I just need to know if one of them has been used and then return the total clicks for that user.
Your understanding of the problem is correct. The join multiplies the rows whenever a user has more than one of the promo codes, and you end up with the same credit summed several times.
I would recommend exists instead:
select cs.userid as name, sum(cs.credits) as totalclicks
from click_stats cs
where cs.source = 'reward' and exists (
select 1
from promo_used pu
inner join promo_codes pc on pc.id = pu.promoid
where
pu.userid = cs.userid
and (pc.name like '%forever%' or pc.name like 'novgfy%')
)
group by cs.userid
having sum(cs.credits) > 10
Let's say i have a user table like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
In the actual, the database consists of more data and some of the data is duplicated, with more than two records. But the point is i want to get only the first and the second row of the duplicated rows that contains the name of "Joseph", How can i achieve this ? My code so far...
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
With that code the result will retrieve :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
And i use this code to try to get the second duplicated row :
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 2')->get();
The result is still same as the mentioned above :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
I want the result is to get record that have the id "5" with name "Joseph" like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
But it seems only the first duplicate row is retrieved and i can't get the second duplicated row, can anybody give me suggestion ?
Let's start from your query
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
This will show all groups of rows whose count equals to 1 ore more. and this is the description of DISTINCT.
If you want to get only duplicate records you should get groups whose count is LARGER than 1.
The other thing to notice here is that a non-aggrigated column will be chosen randomly. because when you get a name and it's count, for example if you select name,count(name), email (email is not in the group by clause - not aggregated), and 4 rows have the same name. so you'll see:
+--------+-------------+-------+
| Name | Count(Name) | Email |
+--------+-------------+-------+
| Joseph | 4 | X |
+--------+-------------+-------+
what do you expect instead of X? which one of the 4 emails? actually, in SQLServer it's forbidden to select a non-aggrigated column and other databases will just give you a random one of the counted 3.
see this answer for more details it's explained very well: Do all columns in a SELECT list have to appear in a GROUP BY clause
So, we'll use having count(name) > 1 and select only the aggregated column name
DB::from('users')->select('name')->groupBy('name')->havingRaw('count("name") > 1')->get();
This should give you (didn't test it) this:
+--------+-------------+
| name | Count(name) |
+--------+-------------+
| Joseph | 4 |
+--------+-------------+
This will give you all names who have 2 or more instances. you can determine the number of duplicates in the having clause. for example having count(name) = 3 will give you all names which have exactly 3 duplicates.
So how to get the second duplicate? I have a question for that:
What is the first (original) duplicate? is it the one with the oldest created_at or the oldest updated_at ? or maybe some other condition?. because of that you should make another query with order by clause to give you the duplicates in the order most convenient to you. for example:
select * from `users` where `name` in (select `name` from users group by `name` having count(`name`) > 1) order by `id` asc
which will give:
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 3 | Joseph | joseph410#mail.com | 21 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
+----+-----------+---------+------------+------+
I have the following table:
TABLE sales
| id | name | date | amount |
|----|------|------------|--------|
| 1 | Mike | 2016-12-05 | 67.15 |
| 2 | Mike | 2016-12-09 | 98.24 |
| 3 | John | 2016-12-12 | 12.98 |
| 4 | Mike | 2016-12-19 | 78.48 |
| 5 | Will | 2016-12-19 | 175.26 |
| 6 | John | 2016-12-22 | 14.26 |
| 7 | John | 2016-12-23 | 13.48 |
I am trying to create a view that will group by the name column and return only the most resent amount. It should look like this:
TABLE sales_view
| id | name | date | amount |
|----|------|------------|--------|
| 4 | Mike | 2016-12-19 | 78.48 |
| 5 | Will | 2016-12-19 | 175.26 |
| 7 | John | 2016-12-23 | 13.48 |
I'm not sure how to go about making this. I would imagine I would need sub-queries, but I know that SQL get mad if you try to use them inside of views.
You can use a tuple and a subquery with group by for max(date)
select * from sales
where (name, date) in ( select name, max(date)
from sales
group by name)
I have tables named Student_Info table, Subject_Info table and an individual table belonging to each student containing information about each subject parameter for that student (like name of the subject, marks he got in that subject etc).
Student_Info
+----+----------+
| Id | Name |
+----+----------+
| 1 | Sam |
| 2 | Taylor |
| 3 | Rick |
+----+----------+
Subject_Info
+---------------+
| Subject_Name |
+---------------+
| Physics |
| Chemistry |
| Mathematics |
+---------------+
1_Info
+---------------+-------+
| Subject_Name | Marks |
+---------------+-------|
| Physics | 60 |
| Chemistry | 40 |
| Mathematics | 80 |
+---------------+-------+
2_Info
+---------------+-------+
| Subject_Name | Marks |
+---------------+-------|
| Physics | 70 |
| Chemistry | 50 |
| Mathematics | 60 |
+---------------+-------+
3_Info
+---------------+-------+
| Subject_Name | Marks |
+---------------+-------|
| Physics | 70 |
| Chemistry | 70 |
| Mathematics | 70 |
+---------------+-------+
Here the tables 1_Info, 2_Info, 3_Info are the tables corresponding to students with Id = 1, Id = 2, Id = 3 respectively.
My questions are
If I insert a subject name into the Subject_Info table I must insert the same subject name in all the individual tables corresponding to each student (1_Info, 2_Info, 3_Info).
I used the following query to get the table name; it works fine.
SELECT CONCAT(Id, '_Info') FROM Student_Info;
I tried to write it using a single query like this
INSERT INTO (SELECT CONCAT(Id, '_Info') FROM Student_Info) VALUES ('Physics');
But getting error.
Is it possibles to do this in single query?
If yes then where am I doing mistake?
Is it a good way to give names to the tables that I am using here for each students subject related parameters (1_Info, 2_Info etc)? If not please suggest a good way.
I think it would be more easy to put the information in 1 Table, like this for example
Student
+----+--------+
| Id | Name |
+----+--------+
| 1 | Sam |
| 2 | Taylor |
| 3 | Rick |
+----+--------+
Subject
+----+-------------+
| Id | Subject |
+----+-------------+
| 1 | Physics |
| 2 | Chemistry |
| 3 | Mathematics |
+----+-------------+
Info
+------------+------------+-------+
| student_id | subject_id | Marks |
+------------+------------+-------+
| 1 | 1 | 60 |
| 1 | 2 | 40 |
| 1 | 3 | 80 |
| 2 | 1 | 70 |
| 2 | 2 | 50 |
| 2 | 3 | 60 |
| 3 | 1 | 70 |
| 3 | 2 | 70 |
| 3 | 3 | 70 |
+------------+------------+-------+
And the INSERT would be
INSERT INTO Student(Name) VALUES('Tom');
INSERT INTO Subject(Subject) VALUES('History');
INSERT INTO Info(4, 4, 80);
EDIT: Alternative, this is what I think is called "Third Normal Form (3NF)"
Student
+----+--------+
| Id | Name |
+----+--------+
| 1 | Sam |
| 2 | Taylor |
| 3 | Rick |
+----+--------+
Subject
+----+-------------+
| Id | Subject |
+----+-------------+
| 1 | Physics |
| 2 | Chemistry |
| 3 | Mathematics |
+----+-------------+
Marks
+----+------+
| Id | Mark |
+----+------+
| 1 | 60 |
| 2 | 40 |
| 3 | 80 |
| 4 | 70 |
| 5 | 50 |
+----+------+
Info
+------------+------------+---------+
| student_id | subject_id | mark_id |
+------------+------------+---------+
| 1 | 1 | 1 |
| 1 | 2 | 2 |
| 1 | 3 | 3 |
| 2 | 1 | 4 |
| 2 | 2 | 5 |
| 2 | 3 | 1 |
| 3 | 1 | 4 |
| 3 | 2 | 4 |
| 3 | 3 | 4 |
+------------+------------+---------+
I have these 3 tables like that:
lecturers:
+-------------+---------+
| id-lecturer | name |
+-------------+---------+
| 1 | Johnson |
| 2 | Smith |
| ... | ... |
| ... | ... |
+-------------+---------+
subjects:
+------------+---------+
| id-subject | name |
+------------+---------+
| 1 | Math |
| 2 | Physics |
| ... | ... |
| ... | ... |
+------------+---------+
exams:
+---------+-------------+------------+------------+
| id-exam | id-lecturer | id-subject | date |
+---------+-------------+------------+------------+
| 1 | 5 | 1 | 1990-05-05 |
| 2 | 7 | 1 | ... |
| 3 | 5 | 3 | ... |
| ... | ... | ... | ... |
+---------+-------------+------------+------------+
When i try to do the first SELECT:
SELECT e.`id-lecturer`, e.`id-subject`, COUNT(e.`id-lecturer`) AS `exams-num`
FROM exams e
JOIN subjects s ON e.`id-subject`=s.`id-subject`
JOIN lecturers l ON e.`id-lecturer`=l.`id-lecturer`
GROUP BY e.`id-lecturer`, e.`id-subject`
I get the right answer. It shows something like that:
+-------------+------------+-----------+
| id-lecturer | id-subject | exams-num |
+-------------+------------+-----------+
| 0001 | 1 | 4 |
| 0001 | 3 | 1 |
| 0001 | 4 | 1 |
| 0001 | 5 | 1 |
| 0002 | 1 | 2 |
| 0002 | 2 | 1 |
| 0002 | 4 | 1 |
| 0002 | 6 | 3 |
+-------------+------------+-----------+
Now i want to show only the max number for every lecturer, my code is:
SELECT it.`id-lecturer`, it.`id-subject`, MAX(it.`exams-num`) AS `exams-number`
FROM (
SELECT e.`id-lecturer`, e.`id-subject`, COUNT(e.`id-lecturer`) AS `exams-num`
FROM egzaminy e
JOIN subjects s ON e.`id-subject`=s.`id-subject`
JOIN lecturers l ON e.`id-lecturer`=l.`id-lecturer`
GROUP BY e.`id-lecturer`, e.`id-subject`) it
GROUP BY it.`id-lecturer`
output:
+-------------+------------+--------------+
| id-lecturer | id-subject | exams-number |
+-------------+------------+--------------+
| 0001 | 1 | 4 |
| 0002 | 1 | 3 |
| 0003 | 1 | 2 |
| 0004 | 1 | 5 |
| 0005 | 2 | 1 |
+-------------+------------+--------------+
I get the correct numbers of the max values for each lecturer, but the subjects id doesn't match, it always takes the first row's id. How can I make it to match correctly these two fields in every row?
I guess you can simply use the same query for further conditions like below.
Select t.Lecturer_id,max(t.exams-num) from
(SELECT e.id-lecturer as Lecturer_id, e.id-subject as Subject_id,
COUNT(e.id-lecturer) AS exams-num
FROM exams e
JOIN subjects s ON e.id-subject=s.id-subject
JOIN lecturers l ON e.id-lecturer=l.id-lecturer
GROUP BY e.id-lecturer, e.id-subject ) as t
group by t.Lecturer_id