一、rollup与cube
1、首先先说明一下何为rollup与cube
rollup：字面意思为上卷,是GROUP BY子句的一种扩展，生成的结果集显示了所选列中值的某一层次结构的聚合，从右至左去掉维度进行小计。
cube：(切片)也是GROUP BY子句的一种扩展，可以返回每一个列组合的小计记录，生成的结果集显示了所选列中值的所有组合的聚合，结果集的总数为2的n次方,其中n为维度的个数。
2、创建测试表
实例操作：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);
插入数据：
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与cube示例
1、rollup
例如group by中有三个维度a,b,c 那么生成的结果则是包含下面的四种情况
select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id with rollup;
一共3中可能的情况:
2、cube
对于cube来说,例如group by中有三个维度a,b,c 那么后续分析的指标则是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个指标。
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极大的简化了sql提高了书写的效率,例如刚才的select id , sku_id,sum(total_amount) from t_order_mt group by id,sku_id with rollup 等价于
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.
原文链接：https://blog.csdn.net/weixin_44080445/article/details/119618144