Tecaher Who Teaches the Most

    

Write an SQL query to fetch the ID of the teacher who takes most number of classes from the table.

Input :-

Class table :-
Class_ID is the Primary Key column for the Class table.

Class_ID	Teacher_ID
1	3
2	3
3	2
4	1

Output :-

Teacher_ID

3

Query :-

select Teacher_ID
from Class
group by Teacher_ID|
order by count(Teacher_ID) desc limit 1;

Explanation : - 

This query is retrieving the Teacher_ID that appears most frequently in the ‘Class’ table. 

The Teacher_ID is grouped and ordered according to the count of the Teacher_ID from the ‘Class’ table in the descending order so that the teacher who takes the most number of classes appears on the top.

Limit 1 limits the result to only one row. In this case, it will return the Teacher_ID with the highest count, as it appears in the first row after ordering.

So, the overall purpose of this query is to find the Teacher_ID that is associated with the most classes in the 'Class' table.