CREATE TABLE IF NOT EXISTS schema.table(
row_id INT(255) NOT NULL AUTO_INCREMENT PRIMARY KEY,
val1 DOUBLE,
val2 DOUBLE,
val3 DOUBLE);

INSERT INTO schema.table (va1, val2) VALUES (1, 2);
INSERT INTO schema.table (va1, val2) VALUES (3, 4);
INSERT INTO schema.table (va1, val2) VALUES (5, 6);

CREATE OR REPLACE
VIEW test_VIEW
AS select
     t1.row_id as row_id,
     if (t1.val3 is null, SUM(t1.val1 + t1.val2) OVER(), t1.val3) AS val3
   from
     test t1