MySQL bit_or () bit_count () function

meaning of the Bit_count function

Used to calculate the number of binary numbers that contain 1.

Select Bit_count (10);

Because 10 turns into binary is 1010, so the result is 2.

meaning of the Bit_or function

is to perform or operate on two binary numbers. Such as:

    1100 or  0101--------------    1101

Example of the MySQL website manual, using Bit_or () Bit_count () to subtly filter out duplicate dates:

The following example shows how can I use the bit group functions to calculate the number of days per month a user have V isited a Web page.

CREATE TABLE T1 (Year of year (4), month int (2) UNSIGNED Zerofill, day             int (2) UNSIGNED Zerofill), INSERT into T1 VALUES (200 0,1,1), (2000,1,20), (2000,1,30), (2000,2,2),            (2000,2,23), (2000,2,23);

The example table contains Year-month-day values representing visits by users to the page. To determine how many different days in each month these visits occur, use this query:

SELECT Year,month,bit_count (Bit_or (1<<day)) as days from T1       GROUP by Year,month;

which returns:

+------+-------+------+| Year | Month | Days |+------+-------+------+| |    |    3 | | |    |    2 |+------+-------+------+

MySQL bit_or () bit_count () function