Удалите НАЧАЛО и КОНЕЦ
CREATE OR REPLACE FUNCTION CSE532.NEIGHBOR_LIST (IN_ZIP VARCHAR(5))
RETURNS TABLE (NEIGHBOR VARCHAR(5))
RETURN SELECT DISTINCT substr(b.GEOID10,1,5) FROM CSE532.USZIP a, CSE532.USZIP b WHERE db2gse.st_intersects(a.SHAPE,b.SHAPE) = 1 AND substr(a.GEOID10,1,5) = IN_ZIP
или используйте НАЧАЛО АТОМИ C
CREATE OR REPLACE FUNCTION CSE532.NEIGHBOR_LIST (IN_ZIP VARCHAR(5))
RETURNS TABLE (NEIGHBOR VARCHAR(5))
BEGIN ATOMIC
RETURN SELECT DISTINCT substr(b.GEOID10,1,5) FROM CSE532.USZIP a, CSE532.USZIP b WHERE db2gse.st_intersects(a.SHAPE,b.SHAPE) = 1 AND substr(a.GEOID10,1,5) = IN_ZIP;
END