>Parent-Child
>3-4
>2-5
>2-6
>2-7

i'm assuming these are the primary key values, and that the child has a foreign key to link to the parent.

select Distinct child.PK, parent.PK ;
       FROM parent join child on parent.PK==child.FK ;
       ORDER by child.PK

the fields will be physically backwards from what you wanted in the output due to the way SQL uses the distinct clause, but field order isn't really important - especially if you're using this Select as the basis for a view (which will likely be interfaced with a grid)