云数据仓库ADB内表字段定义not null会导致已经导入的数据逐渐减少吗？

云数据仓库ADB内表字段定义not null会导致已经导入的数据逐渐减少吗？
create table catalog_returns
(
cr_returned_date_sk bigint,
cr_returned_time_sk bigint,
cr_item_sk bigint not null,
cr_refunded_customer_sk bigint,
cr_refunded_cdemo_sk bigint,
cr_refunded_hdemo_sk bigint,
cr_refunded_addr_sk bigint,
cr_returning_customer_sk bigint,
cr_returning_cdemo_sk bigint,
cr_returning_hdemo_sk bigint,
cr_returning_addr_sk bigint,
cr_call_center_sk bigint,
cr_catalog_page_sk bigint ,
cr_ship_mode_sk bigint ,
cr_warehouse_sk bigint ,
cr_reason_sk bigint ,
cr_order_number bigint not null,
cr_return_quantity double,
cr_return_amount double,
cr_return_tax double,
cr_return_amt_inc_tax double,
cr_fee double,
cr_return_ship_cost double,
cr_refunded_cash double,
cr_reversed_charge double,
cr_store_credit double,
cr_net_loss double
)
DISTRIBUTE BY HASH(cr_item_sk)
PARTITION BY VALUE(JULIAN_DATE_TO_YEAR_MONTH(cr_returned_date_sk)) PARTITION NUM 1000;