select top 10 students from database [duplicate] - mysql

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Closed 11 years ago.
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sql to select top 10 records
Assuming you have one table with StuId, StuName, Subject, Grade. You are required to provide a subquery to return a list of honor students (top 10 percent), sorted by their grade point average.
for example, if I have 10 student whose average grade is 100,90,80,...10.
It is required to output the first student name whose average is 100. Only one student grade is output. So I can't use limit 10
I am using mysql 5.1.
Here is my query:
SELECT Stuname, TOP 10 Avg(Grade) as GPA
FROM Table
GROUP BY Stuid
ORDER BY GPA
The query is not correct because of the TOP 10. Checking MYSQL 5.1 reference, it does not support top 10.
According to comments, I dont think it can be resolved using one query, so I come up with a method:
F(conn){
Statement stmt;
int top10percnet = 0;
try{
stmt = conn.createStatement;
String query = "select CEIL(count(stuname)*10/100) as 10percent from grades";
ResultSet rs = stmt.execute(query);
while(rs.next()){
top10percent = rs.getString("10percent");
}
query = "select stuname, avg(grade) as average from grades group by stuname order
by average desc limit " + Integer.toString(top10percnet);
rs=stmt.execute(query);
while(rs.next()){
...// output result
}
}
catch(SQLException e){
}
}

Answer 1

count = select CEIL(count(Stuname)*10/100) from table_name;
select Stuname from table_name ORDER BY GPA DESC limit count;
First query will return the 10% of the students.CEIL is used to convert it into integer.
Second query is to retrieve the data.
The count calculated from the first query is set as the limit to the second query.

Answer 2

Use LIMIT and DESC order (ie highest to lowest):
select Stuname, Avg(Grade) as GPA
from Table
group by Stuid
order by 1 DESC -- Add DESC
LIMIT 10 -- Add LIMIT

Answer 3

Update
Sounds like you want to incorporate a HAVING clause to limit the results to those scoring an average grade higher than 90.
Try
SELECT Stuid, Stuname, AVG(Grade) AS GPA FROM Table
GROUP BY Stuid, Stuname
HAVING AVG(GRADE) > 90
ORDER BY GPA DESC -- If you want highest-to-lowest. Thanks Bohemian

Answer 4

TOP is SQL Server 2000+ specific; MySQL uses the LIMIT syntax -- neither are ANSI, only recently was the FETCH FIRST 10 ROWS ONLY made ANSI (DB2 is the only DB I know of that supports it).
Because you tagged the question as "mysql":
SELECT t.stuname,
AVG(t.grade) AS grade_avg
FROM TABLE t
GROUP BY t.stuname
ORDER BY grade_avg DESC
LIMIT 10
For SQL Server 2000+, the query would be:
SELECT TOP 10
t.stuname,
AVG(t.grade) AS grade_avg
FROM TABLE t
GROUP BY t.stuname
ORDER BY grade_avg DESC
TOP is always before the columns in the SELECT clause. As of SQL Server 2005+, you can use brackets around the top value to allow you use a variable instead:
DECLARE #int_var INT
SET #int_var = 10
SELECT TOP (#int_var)
t.stuname,
AVG(t.grade) AS grade_avg
FROM TABLE t
GROUP BY t.stuname
ORDER BY grade_avg DESC
This allows you dynamically set the TOP without requiring dynamic SQL.

Answer 5

Have you tried using LIMIT instead?
e.g.
select Stuname, Avg(Grade) as GPA from Table group by Stuid order by GPA limit 10