Shuold I use not exists or join statement to filter out NULLs?

Question

SELECT  *
FROM    employees e
WHERE   NOT EXISTS
        (
        SELECT  name 
        FROM    eotm_dyn d
        WHERE   d.employeeID = e.id
        )

Answer 1

Assuming the column values involved can not be NULL -

MySQL:

LEFT JOIN/IS NULL is more efficient than NOT EXISTS - read this article for details.

Oracle:

They are equivalent.

SQL Server:

NOT EXISTS is more efficient than LEFT JOIN/IS NULL - read this article for details.

Postgres:

Like Oracle, they are equivalent.

If you have trouble with the detail that the column values can not be null, yet use the LEFT JOIN / IS NULL - remember what a LEFT JOIN signifies. This link might help.