bitmap_union

description

Aggregate function, used to calculate the grouped bitmap union. Common usage scenarios such as: calculating PV, UV.

Syntax

BITMAP BITMAP_UNION(BITMAP value)

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

example

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

Combined with the bitmap_count function, the PV data of the web page can be obtained

mysql> 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

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

keyword

BITMAP_UNION, BITMAP