CODEWITHSUNDEEP
pivot-tableclickhouse
Amit
Amit

Reputation: 35

Pivot or equivalent in clickhouse

I'm new to clickhouse or for that matter in any columnar db. I need to pivot the table like we do in sql-server, postgres or any other row based db.

I'm looking for a generic solution however solution to the example here will do well.

Table: Store

Tag  Slot  Reading  
---  ---- --------      
A     1     5 
B     1     6  
C     1     1  
A     2     2       
B     2     8
C     3     2
.
.
millions of rows

Transpose to: 

Slot  A   B   C   and so on  
---   --  --  --       
1     5   6   1
2     2   8   -  
3     -   -   2  
.
. 
and so on

tags can be anywhere between 100 to 1000, slots can be between 1000-10000. But it doesn't matter.

I need to do this using sql only.

Thanks.

Upvotes: 2

Views: 7253

Answers (2)

Denny Crane
Denny Crane

Reputation: 13310

create table xxx (Tag String, Slot Int64, Reading Int64) Engine=Memory;
insert into xxx values 
('A',1,5),
('B',1,6), 
('C',1,1),  
('A',2,2),  
('B',2,8),
('C',3,2)

SELECT
    Slot,
    groupArray((Tag, Reading))
FROM xxx
GROUP BY Slot

┌─Slot─┬─groupArray(tuple(Tag, Reading))─┐
│    3 │ [('C',2)]                       │
│    2 │ [('A',2),('B',8)]               │
│    1 │ [('A',5),('B',6),('C',1)]       │
└──────┴─────────────────────────────────┘

Upvotes: 3

Denny Crane
Denny Crane

Reputation: 13310

select Slot, 
       sumIf(Reading, Tag='A') A,
       sumIf(Reading, Tag='B') B,
       ...
group by Slot

select Slot, arrayReduce('sumMap', [(groupArray(tuple(Tag,Reading)) as a).1], [a.2])
...
group by Slot

select Slot, groupArray(tuple(Tag, Reading))
from 
  (select Slot, Tag, sum(Reading) Reading
  ...
  group by Slot, Tag)
group by Slot

Upvotes: 0

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