MySQL searches and sorts out common methods according to time

1. Use date_sub

Inquire about 3 Days of data

select * from mytable where update_time > date_sub(curdate(),interval 3 DAY)

here ,update_time by datetime、date、timestamp Equal type time , have access to .

2. Use to_days

Inquire about 3 Days of data

select * from mytable where 3 > to_days(now())-to_days(update_time)

here ,update_time by datetime、date、timestamp Equal type time , have access to .

3. The method of converting time into characters ,DATE_FORMAT

select DATE_FORMAT(update_time, '%Y-%m-%d %H:%i:%S')  from mytable

4. The method of character to time ,STR_TO_DATE

select  str_to_date('2022/06/24','%Y/%m/%d');

5. Character to time to turn Timestamp Methods ,UNIX_TIMESTAMP（ Not commonly used ）

select  UNIX_TIMESTAMP(str_to_date('2022/06/24','%Y/%m/%d'));

Be careful , This method is not commonly used ; If you want to put the datetime、date Type of data can be found 、 Save to timestamp Column , Just save it directly , There is no need to convert ;
If you want to query the data of character type 、 Save to timestamp Column , Just convert to time type 、 And save it , There is no need to convert to timestamp; Errors will be reported after conversion .（kettle Found during data extraction ）