建表如下：
# 创建商品与促销活动的映射表hive -e "set mapred.job.queue.name=pms;set hive.exec.reducers.max=32;set mapred.reduce.tasks=32;drop table if exists product_promotion;create table product_promotion(product_id bigint, promotion_id String);insert into table product_promotion select p2.product_id, p2.promotion_id from pms.promotionv2 p1 inner join pms.promotionv2_main_product_sku p2 on (p1.id=p2.promotion_id)where from_unixtime(unix_timestamp(),'yyyy-MM-dd HH:mm:ss') between p1.start_date and p1.end_date;"
数据表的记录如下： 对promotion_id进行合并：
select product_id, concat_ws('_',collect_set(promotion_id)) as promotion_ids from product_promotion group by product_id
执行结果：
hive > select product_id, concat_ws('_',collect_set(promotion_id)) as promotion_ids from product_promotion group by product_id;OK5112 960024_960025_960026_960027_9600285113 960043_960044_960045_960046Time taken: 3.116 seconds
这里的collect_set的作用是对promotion_id去重，值得注意的是，必须保证promotion_id的类型是string类型
