Question

In this query I need to remove duplication tutor id and counting them..

SELECT COUNT(t.tutor_id) FROM tutors AS t
    INNER JOIN tutor_category_subject as tcs ON t.tutor_id = tcs.tutor_id   
    INNER JOIN subject AS s ON tcs.subject_id = s.subject_id
WHERE s.subjects LIKE '%business%' 

this is query output:

+-------------------+
| COUNT(t.tutor_id) |
+-------------------+
|                 6 |
+-------------------+

but it should be 4.. why there tutor ids are 3, 6, 15, 15, 16, 16

Answer 1

Use distinct

SELECT COUNT(DISTINCT t.tutor_id) FROM tutors AS t
    INNER JOIN tutor_category_subject as tcs ON t.tutor_id = tcs.tutor_id   
    INNER JOIN subject AS s ON tcs.subject_id = s.subject_id
WHERE s.subjects LIKE '%business%'