i need help on this, can someone please look at this,

let's say there are two tables on my database
1. category table having column id with values like 1 to 10
2. details table having column category with the values like 2, 4, 6, 8, 10

so i want to list 5 values from category table's id columns but only those values that are in details table category column,

how do i do it pls guide me.