questions encountered in the interview
, a praise form, with id self-increasing primary key, w_id article id,create_time like time (in the form of 11:50:22 2018-10-02). Ask for the number of likes per article per day between 10.1 and 10.10
questions encountered in the interview
, a praise form, with id self-increasing primary key, w_id article id,create_time like time (in the form of 11:50:22 2018-10-02). Ask for the number of likes per article per day between 10.1 and 10.10
this topic is quite disgusting. For a contestant like me who usually has to try SQL several times and Baidu can only write it out, there must be mistakes in handwriting.
this requires
count , no doubt
date_format , or other methods for dealing with dates, such as string interception, which is not expanded here. It is used to convert the time in the database into a date string.
group by , The number of likes per article per day, that is, the total number of entries that appear count , which are grouped by article and date.
this is what the train of thought looks like.
SELECT
DATE_FORMAT(`create_time`, '%Y-%m-%d') as `day`,
`w_id`,
COUNT(1)
FROM `dianzan`
GROUP BY `day`, `w_id`;
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