CREATE FUNCTION FuncTest1 ()
    RETURNS TABLE
    (
        USE_NAME VARCHAR(48),
        USE_PARTNER_LINK FLOAT
    )
        LANGUAGE SQL
        MODIFIES SQL DATA
        DETERMINISTIC
        BEGIN
        DECLARE GLOBAL TEMPORARY TABLE USE_TRUNC
        (
           USE_NAME VARCHAR(48) NULL,
           USE_PARTNER_LINK FLOAT NULL
        );
        INSERT INTO SESSION.USE_TRUNC
            (USE_NAME,USE_PARTNER_LINK)
        SELECT USE_NAME,USE_PARTNER_LINK FROM F_USERS;
        RETURN
        SELECT USE_NAME,USE_PARTNER_LINK FROM F_USERS;
        END

An unexpected token "USE_NAME" was found following "
  RETURN
  SELECT".  Expected tokens may include:  "(".. SQLCODE=-104, SQLSTATE=42601, DRIVER=4.9.78