SELECT DISTINCT or array_unique?

Question

What do you think is faster?

SELECT DISTINCT(user_id) FROM myTable;

Then fetch to $myArray.

Or

SELECT user_id FROM myTable;

Then fetch to $myArray and do

$myArray = array_unique($myArray);

Note: user_id is a FOREIGN KEY CONSTRAINT

Answer 1

For speed and memory efficiency, you want to return the minimum amount from the database without putting unnecessary rows for processing/memory efficiency. So, the distinct in this case is the better choice.