PostgreSQL version

UPDATE    tbl_data 
SET    lov_id =  randomizer.lov_id
FROM    (
    SELECT DISTINCT
        data_id,
        FIRST_VALUE(lov_id) OVER (PARTITION BY data_id ORDER BY seed) AS lov_id
    FROM    (
        SELECT    tbl_data.data_id, tbl_lov.lov_id, RANDOM() AS seed
        FROM    tbl_data
        CROSS JOIN tbl_lov
    ) seeder
) randomizer 
WHERE    tbl_data.data_id = randomizer.data_id;