I have two tables
table1
Name marks
John 50
Smith 70
Adam 60
Roy 70
table2
Score Grade other
50 C 1.5
60 B 0.7
70 A 0.8
70 A 1.0
I want to get how many people have got A, B, C passes
I want to get an output as
Grade Count
C 1
B 1
A 2
Query I tried was
SELECT table2.Grade,
COUNT(DISTINCT table2.Grade) as count
FROM table1
LEFT JOIN table2
ON table1.Mark = table2.Score
GROUP BY table2.Grade;
But it Gives
Grade Count
C 1
B 1
A 4
So How to remove the duplicates ?
Please help.
At your second table, you got duplicate rows:
Score Grade other
50 C 1.5
60 B 0.7
70 A 0.8
70 A 1.0
Here, there are to A's, and when you joing with first table according to the field "Grade--Score", the whole join is:
Jhon 50 C
Smith 70 A
Smith 70 A --> Second A from second table
Adam 60 B
Roy 70 A
Roy 70 A --> Second A from second table
So group by and count will result 4 for the field grade here:
A 4 --> 2 Smith and 2 Roy
B 1
C 1
So, to get how many single person per grade:
select tb2.Grade GradeMark, count(*) TotalPersons
from table1 as tb1
left join (select tbi2.Score, distinct(tbi2.Grade), tbi2.other, from table2 tbi2) as tb2 on tb2.Grade = tb1.marks
group by tb2.Grade
This query will select distinct values from table2, join with table one and count the results per grade so you should get:
A 2
B 1
C 1
You don't need a JOIN for this. You can try like below using a simple group by and get the count()
select Grade, count(*) as `Count`
from table2
group by Grade;
Related
I have two tables:
Table A
ID Number Profile
1 100 Baker
2 75 Fields
3 100 Wayward
Table B
ID Number Tag Sender
1 50 on chris
2 50 off james
What I am try to do subtract the values from Table A and Table B who has the same ID numbers
Table C
ID Number
1 50
2 25
SELECT A.ID,A.NUMBER-B.NUMBER DIFF
FROM TABLE_A AS A
JOIN TABLE_B AS B ON A.ID=B.ID
Hello I have the following tree tables and I want to achieve the Table named "wanted result".
On the first are the house names, on the second the name of the rooms of each house and on the third the price of each room.
I want a count of rooms by house.
table_1
nid name
1 House 1
2 House 2
3 House 3
table_2
Name house_ref_id id
Room1 1 20
Room1 2 21
Room1 2 22
Room1 3 23
Room1 3 24
table_3
Price room_ref_id
0 20
100 21
150 22
0 23
120 24
Wanted result:
nid name Rooms w/ price
1 House1 0
2 House2 2
3 House3 1
I have tried the following code but could get the right amount of rooms with price
SELECT Name, COUNT(price) AS "rooms w/ price" FROM table_1
LEFT JOIN table_2 ON table_1.id = table_2.ref_id
LEFT JOIN table_3 ON table_2.room_ref_id = table_3.id
WHERE table_3.price>0
GROUP BY table_1.nid
but got the following:
nid name rooms w/ price
1 nouse1 1
2 house2 2
3 house3 2
Close. The condition in the WHERE turns the outer joins into inner joins. You need to move it to the ON clause:
SELECT Name, COUNT(table3.id) AS "rooms w/ price"
FROM table_1 LEFT JOIN
table_2
ON table_1.id = table_2.ref_id LEFT JOIN
table_3
ON table_2.room_ref_id = table_3.id AND table_3.price > 0
GROUP BY table_1.nid;
I have two tables. One is the Course table and the second is the Teacher table. I want to get all Teacher who does not teach 'Math'. How can I do this?
Course Table
course_id course teacher_id marks
1 Physics 1 60
2 Math 1 60
3 Chemestry 1 60
4 English 2 60
5 Hindi 2 60
6 Physics 2 60
7 Chemestry 3 60
8 English 4 60
9 Math 5 60
10 Math 6 60
Teacher Table
teacher_id name salary gender
1 Teacher1 20 1
2 Teacher2 30 1
3 Teacher3 40 2
4 Teacher4 50 2
5 Teacher5 60 1
6 Teacher6 70 2
I want to get all teacher who does not teachs math.
You need to join both the tables on teacher_id and then filter out the rows based on the course.
SQL> SELECT DISTINCT t.name
2 FROM course c,
3 teacher t
4 WHERE c.teacher_id = t.teacher_id
5 AND c.course <> 'Math';
NAME
--------
Teacher2
Teacher1
Teacher4
Teacher3
SQL>
EDIT Since you have teachers teaching multiple courses, you need to filter out further:
SQL> WITH DATA AS
2 (SELECT c.*,
3 t.name
4 FROM course c,
5 teacher t
6 WHERE c.teacher_id = t.teacher_id
7 AND c.course <> 'Math'
8 )
9 SELECT DISTINCT name
10 FROM data
11 WHERE teacher_id NOT IN
12 (SELECT teacher_id FROM course WHERE course = 'Math'
13 )
14 /
NAME
--------
Teacher2
Teacher4
Teacher3
SQL>
NOTE Please keep in mind that the other solution using NOT EXISTS clause is better in terms of performance, since the table scans are less and even index scans. With proper indexes, the not exists query would be an optimal method.
select *
from teacher t
where not exists
(select 1 from course c where c.teacher_id = t.teacher_id and c.course = 'Math')
#LalitKumarB
Ben is absolutely right
inner join
select t.teacher_id, t.name
from teacher t, Course c
where c.course='math' and t.teacher_id=c.teacher_id;
EDIT
you can do it using join and subquery.
select * from course join teacher
on course.teacher_id=teacher.teacher_id
where teacher.teacher_id not in
(select distinct teacher_id from course where course = 'Math')
Select * from Teacher
join Course
on Teacher.teacher.id = Course.teacher.id
where Course.course != 'Math'
select
t.name
from teacher t
left join course c
on c.teacher_id = t.teacher_id
where c.course_id <> 2
I would like to know how to retrieve rows matching the maximum value for a column.
SCHEMA
assignments:
id student_id subject_id
1 10 1
2 10 2
3 20 1
4 30 3
5 30 3
6 40 2
students:
id name
10 A
20 B
30 C
subjects:
id name
1 Math
2 Science
3 English
Queries:
Provide the SQL for:
1. Display the names of the students who have taken most number of assignments
2. Display the names of the subjects which have been taken the most number of times
Results:
1.
A
C
2.
Math
English
Thanks !
The previous answer is not quite right - you won't get the instances where there are two with the same count. Try this - the second will be easy to replicate once understand the concept.
SELECT a.student_id, s.name, COUNT(a.subject_id) as taken_subjects
FROM assignments a
INNER JOIN students s ON a.student_id = s.id
GROUP BY a.student_id, s.name
HAVING COUNT(a.subject_id) = (SELECT COUNT(*) FROM assignments GROUP BY student_id LIMIT 1)
Alternate query:
SELECT a.subject_id, s.subject_name, COUNT(a.subject_id) FROM assignment a, subjects s
WHERE a.subject_id = s.subject_id
GROUP BY a.student_id, s.subject_name
HAVING COUNT(a.subject_id) = (SELECT MAX(COUNT(1)) FROM assignment GROUP BY subject_id)
I have two tables. I want to select id from table 1 and count the same from table2
Table 1
Id qId opt
1 30 Chris Christie
2 30 Hillary Clinton
3 30 Allan West
4 30 Joe Biden
5 31 Mark
6 31 Ben Johnson
Table2
poll_id qId ansId
201 30 1
202 30 2
204 31 8
The below query i tried, outputs only the ansId 1 and 2 since there is no 3 and 4 in Table2.
SELECT a.Id,
a.opt,
COUNT(b.ansId)
from Table1 a
INNER JOIN Table2 b ON a.Id = b.ansId
where a.qId =30
But i need all ansId 1,2,3,4 with count of 3 and 4 as 0 as given below.
Id opt COUNT(b.ansId)
1 Chris Christie 1
2 Hillary Clinton 1
3 Allan West 0
4 Joe Biden 0
First thing your are missing with group by ,count is an aggregate function and this needs to be grouped,second you need to use left join with an additional condition in on clause i.e and a.qId =30 so it will stil gives you the result if left id is not found in right table,using where clause will filter out the whole resultset while if you use additional condition in join this will only filter the records from the right table
SELECT a.Id,
a.opt,
COUNT(b.ansId) from Table1 a
LEFT JOIN Table2 b ON a.Id = b.ansId and a.qId =30
GROUP BY a.Id
Fiddle Demo
Edit after sample dataset is updated
SELECT a.Id,
a.opt,
COUNT(b.ansId) from Table1 a
LEFT JOIN Table2 b ON a.Id = b.ansId
WHERE a.qId =30
GROUP BY a.Id
Fiddle demo 2