Question

I’d like to do a left join using only certain rows of the first table in mysql. Currently I do something like:

SELECT students.* FROM students             
LEFT JOIN courses                           
ON students.id = courses.id                 
WHERE students.id = 6

But will mysql first select rows from table1 (students) satisfying students.id = 6, before doing the left join?
If not, is there a way to force mysql do to so?
Thanks.

Answer 1

Yes there is, try this:

SELECT students.* FROM students             
LEFT JOIN courses                           
ON students.id = courses.id                 
HAVING students.id = 6
LIMIT 1