Count in selected query

Question

I have the following query:

select exam_id,semester_id from marks where student_id=150 and semester_id<=1914; 

His conclusion:

 exam_id | semester_id 27 1913 68 1913 64 1914 

I want to find out the number of similar semester_id .

when i try mysql_num_rows it shows 3.

But I want it to look like

  semester_id 1913---------->count 2 semester_id 1914---------->count 1 

Answer 1

You just use GROUP BY :

 SELECT semester_id, COUNT(*) as count FROM marks WHERE student_id=150 AND semester_id<=1914 GROUP BY semester_id; 

Answer 2

try it

 select semester_id,count(*) as cnt from marks where student_id=150 and semester_id<=1914 group by semester_id; 

Answer 3

Use the aggregate function Count() that you can achieve.

  SELECT semester_id, COUNT(exam_id) FROM marks WHERE student_id=150 AND semester_id<=1914 GROUP BY semester_id; 

Answer 4

 Select semester_id, count(exam_id) From marks Group By semester_id; 

if you feel the need, use:

 count(distinct exam_id) 

Answer 5

Use count ()

 SELECT semester_id, COUNT(*) as count FROM marks WHERE student_id=150 AND semester_id<=1914 GROUP BY semester_id;