bitmap_union
Description
Calculates the bitmap union of a set of values after grouping. Common usage scenarios include calculating PV and UV.
Syntax
BITMAP BITMAP_UNION(BITMAP value)
Examples
select page_id, bitmap_union(user_id)
from table
group by page_id;
Use this function with bitmap_count() to obtain the UV of a web page.
select page_id, bitmap_count(bitmap_union(user_id))
from table
group by page_id;
If user_id
is an integer, the above query statement is equivalent to the following:
select page_id, count(distinct user_id)
from table
group by page_id;
keyword
BITMAP_UNION, BITMAP