一、rollup與cube
1、首先先說明一下何為rollup與cube
rollup：字面意思為上卷,是GROUP BY子句的一種擴展，生成的結果集顯示了所選列中值的某一層次結構的聚合，從右至左去掉維度進行小計。
cube：(切片)也是GROUP BY子句的一種擴展，可以返回每一個列組合的小計記錄，生成的結果集顯示了所選列中值的所有組合的聚合，結果集的總數為2的n次方,其中n為維度的個數。
2、創建測試表
實例操作：ck中建如下表
create table t_order_rmt(
id UInt32,
sku_id String,
total_amount Decimal(16,2) ,
create_time Datetime
) engine =ReplacingMergeTree(create_time)
partition by toYYYYMMDD(create_time)
primary key (id)
order by (id, sku_id);
插入數據：
insert into t_order_mt values
(101,'sku_001',1000.00,'2020-06-01 12:00:00'),
(101,'sku_002',2000.00,'2020-06-01 12:00:00'),
(103,'sku_004',2500.00,'2020-06-01 12:00:00'),
(104,'sku_002',2000.00,'2020-06-01 12:00:00'),
(105,'sku_003',600.00,'2020-06-02 12:00:00'),
(106,'sku_001',1000.00,'2020-06-04 12:00:00'),
(107,'sku_002',2000.00,'2020-06-04 12:00:00'),
(108,'sku_004',2500.00,'2020-06-04 12:00:00'),
(109,'sku_002',2000.00,'2020-06-04 12:00:00'),
(110,'sku_003',600.00,'2020-06-01 12:00:00');
二、rollup與cube示例
1、rollup
例如group by中有三個維度a,b,c 那么生成的結果則是包含下面的四種情況
select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id with rollup;
一共3中可能的情況:
2、cube
對於cube來說,例如group by中有三個維度a,b,c 那么后續分析的指標則是group by , group by a , group by b ,group by c , group by a,b ,group by a,c group by b,c ,group by a,b,c 共8個指標。
cube操作:
select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id with cube;
clickhouse中的with rollup 和with cube極大的簡化了sql提高了書寫的效率,例如剛才的select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id with rollup 等價於
select id , sku_id,sum(total_amount) from t_order_mt
union on
select id , sku_id,sum(total_amount) from t_order_mt group by id
union on
select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id.
原文鏈接：https://blog.csdn.net/weixin_44080445/article/details/119618144