在MySQL中存储日期

Question

Is it better to store dates in mysql in three columns or use just one column. Which one is faster. Also, if I just want to do inserts with todays date in format dd/mm/yy , how do I do that. and also how do I do selects with that. Also, lets say if I wanted to get results for all the wednesdays, how do I do that or lets say one date 25th of all the months and years, how do i do that.

Thanks People.

I am using PHP with Apache and Mysql.

What are the drawbacks of using the structure that I am proposing. I can easily get all the 25th by using the date table and I can get all the days using another column for days. How much difference would be there in the terms of speed between my proposed solution and using a DATE table?

Answer 1

You will want to use a proper column type, such as DATE , DATETIME , or TIMESTAMP , depending on your needs. They are built specifically to handle dates, and can more easily perform other functions (adding, comparing, etc.) that would be difficult to perform on 3 separate columns.

Read this for more info.

DAYOFWEEK(date) will give you a numeric representation for the day. In your case, 4 = Wednesday. DAYOFMONTH(date) will work for finding all 25th days of the month.

DAYNAME(date) will return the name of the weekday for date

Answer 2

Also, if I just want to do inserts with todays date in format dd/mm/yy ,how do I do that.

Well it depends on the format your date is passed in through your 
form but you are going to want to store your date in YYYY-mm-dd format.

INSERT INTO my_table (timefieldname) VALUES ( '$date' );

and also how do I do selects with that.

SELECT timefieldname FROM my_table;

//or you can format the date - this will give you month/day/year 01/01/2012
SELECT DATE_FORMAT(timefieldname, '%m/%d/%Y') FROM my_table;

Also, lets say if I wanted to get results for all the wednesdays,

SELECT timefieldname FROM my_table WHERE DAYNAME(timefieldname) = 'Wednesday';

How do I do that or lets say one date 25th of all the months and years, how do i do that.

SELECT timefieldname FROM my_table WHERE DAY(timefieldname) = '25'; 

Answer 3

You can free up having to pass dates from your codebase and let mysql insert them for you, provided they are time stamps:

ALTER TABLE tablename ADD `timefieldname` TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ;

It's not much of a speed boost, but it does reduce your need to code and validate variables passed to the database.