两周前选择查询

Question

In my database table I have a field for date (varchar field to save date in yy-mm-dd format ), now I want to select records for two weeks ago. How can i do it ?

Answer 1

Implicit date arithmetic is fairly flexible in MySQL. You can compare dates as strings without explicit use of CAST() or DATE() , but you're trusting MySQL to interpret your format correctly. Luckily for you, it will do just fine with yy-mm-dd .

I would recommend using BETWEEN and INTERVAL so that your query is easily readable; for example:

SELECT * FROM Holidays 
WHERE Date BETWEEN (NOW() - INTERVAL 14 DAY) AND NOW();

The only trick with BETWEEN is that you have to put the lower bound first and the upper bound second; for example, if you write BETWEEN 5 AND 2 , this always evaluates to FALSE because there is no value that can be greater than or equal to 5 while also being less than or equal to 2.

Here's a demo of the query in action at SQL Fiddle , and a list of the recognized INTERVAL expressions in MySQL.

Note that the parentheses around the expression NOW() - INTERVAL 14 DAY are not required but I would recommend using them here purely for the sake of clarity. It makes the predicate clause just a little bit easier to read in the absence of proper syntax highlighting, at the expense of two characters.

Answer 2

Ideally you should be using date types to store dates, but being that's not the case, you should look into casting to date then comparing.

select * from yourtable where cast (yourdate as Date) BETWEEN Date_Add(CURDATE(), INTERVAL -21 Day) and Date_Add(CURDATE(), INTERVAL -14 Day)

Note, this is untested and may need a little tweaking, but should give you a general idea of what you need to do.

Also, if it's possible, you should really look into converting the varchar field to a date field....they have date types to prevent this sort of thing from happening, although i know changing field types isn't always a possibility.

Answer 3

you can simply do with ADDDATE to get 14 days ago. compare string with date will work.

SELECT *
FROM your_table
WHERE your_date >= ADDDATE(NOW(), -14) AND your_date < NOW()

Answer 4

I use this for select data in past of past

SELECT * FROM Holidays 
WHERE a.dDate >= DATE( NOW( ) ) - INTERVAL 14
DAY AND a.dDate <= DATE( NOW( ) ) - INTERVAL 8