I have two tables which form a 1:many relationship.

For example,
The main table A can be:

1 ParentA graduate
2 ParentB doctor
3 ParentC engineer

and Child table can be

1 1 ChildA1 6th grade
2 1 ChildA2 graduate
3 1 ChildA3 engineer
4 2 ChildB1 doctor

Now you see, that parentA has three childs, parentB has 1 and parentC has none.

I would like to know those parents who are engineers or whose children might be engineers.

So I tried a query like
But this query is leaving out the parent who doesn't have a child. How do I do this?

I believe you should be using a LEFT OUTER JOIN.