How to count rows in one table based on another table in mysql

Question

I have two tables in a MySQL database. The first one has a list of department names.

departments
    abbreviation | name
    -------------|-------------
             


        

Answer 1

Try this

SELECT d.abbreviation, COUNT(*) num
FROM departments d
INNER JOIN courses c ON c.section LIKE CONCAT(d.abbreviation, "%")
GROUP BY d.abbreviation

Answer 2

SELECT d.abbreviation, COUNT(*) num
FROM departments d
INNER JOIN courses c ON c.section LIKE CONCAT(d.abbreviation, "%")
GROUP BY d.abbreviation

Sql Fiddle

Answer 3

I quick solution, but not the best, could be:

SELECT abbreviation, 
(SELECT COUNT(*) FROM courses C WHERE D.abbreviation = SUBSTRING(C.abbreviation, 0, 3)) AS c 
FROM departments D;

Answer 4

Give this a shot:

select
    d.abbreviation,
    count(d.abbreviation) count
from
    departments d
inner join
    courses c
on (LOCATE(d.abbreviation,c.section) <> 0)
group by d.abbreviation;