bitmap_union

description

Aggregation function, used to calculate the bitmap union after grouping. Common usage scenarios: calculating PV and UV.

Syntax

BITMAP BITMAP_UNION(BITMAP value)

Enter a set of bitmap values, calculate the union of this set of bitmap values, and return the result.

example

select page_id, bitmap_union(user_id)
from table
group by page_id;

Use with bitmap_count function to obtain the PV data of the web page:

select page_id, bitmap_count(bitmap_union(user_id))
from table
group by page_id;

When the user_id field is int, the above query semantics is equivalent to:

select page_id, count(distinct user_id)
from table
group by page_id;

keyword

BITMAP_UNION, BITMAP