4.6.8 Calculating Visits Per Day

使用ZEROFILL,数字<10时，将数字自动补0

The following example shows how you can use the bit group functions to calculate the number of days per month a user has visited a Web page.

CREATE TABLE t1 (year YEAR(4), month INT(2) UNSIGNED ZEROFILL, day INT(2) UNSIGNED ZEROFILL); INSERT INTO t1 VALUES(2000,1,1),(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 | +——+——-+——+ | 2000 | 01 | 3 | | 2000 | 02 | 2 | +——+——-+——+