MySQL - Using JOIN and WHERE to determine average hours

Question

I am learning MySQL using a next.tech course that relies on the following schema:

My current task is to find the average number of hours worked on one specific

Answer 1

In the above Query, you are trying to compare employee_id and project_id, i think that might be the issue. Make sure that you are using JOIN correctly with attributes.

Thank you for reading!! Happy Learning!!

Answer 2

The where clause must come after join, not before

Answer 3

You need specific wich join you using, there's INNER,LEFT,RIGHT,FULL,OUTER So try these

SELECT AVG(hours) FROM project_employees
INNER JOIN  projects
ON  project_employees.employee_id = projects.id
WHERE name = 'Washington Avenue Barber';

Answer 4

The syntax of your SQL query seems to be the main problem behind the first error.

you are doing SELECT-FROM-WHERE-JOIN, but the actual sequence should be SELECT-FROM-JOIN-WHERE.

Your second query (which is returning a wrong value) has the correct syntax, which is why it returns something.

Secondly, you should be comparing projects.id with project_employees.project_id, not project_employees.employee_id. Therefore, your query should be something like -

SELECT AVG(hours) FROM project_employees
JOIN  projects
ON  project_employees.project_id = projects.id
WHERE name = 'Washington Avenue Barber';