Does MySQL provide any function which verifies the validity of a date? The DATE function returns NULL upon provision of the invalid date 2013-02-30 for example. However, I am also using STR_TO_DATE simultaneously, which mysteriously stops DATE from working correctly.
SELECT DATE('2013-02-30'); NULL
SELECT STR_TO_DATE('2013-02-30', '%Y-%m-%d'); NOT NULL
SELECT DATE('2013-02-40'); NULL
SELECT STR_TO_DATE('2013-02-40', '%Y-%m-%d'); NULL
SELECT DATE(STR_TO_DATE('2013-02-30', '%Y-%m-%d')); NOT NULL
Why does STR_TO_DATE halt DATE's functionality and is there some workaround to verify if a date is valid when using STR_TO_DATE (which I am obligated to use)?
I have stumbled upon the answer in the meantime: apparently the DATE function skips a few validation checks, when the data type is already that of 'date' (STR_TO_DATE converts strings to date data types). Therefore, converting the date to a string after having parsed it to the correct format with STR_TO_DATE, does the trick:
#valid_date = NOT ISNULL(DATE(CONVERT(STR_TO_DATE('2013-02-29', '%Y-%m-%d'), CHAR))).
It is very difficult to verify if a field is a date because of all the different possible date formats that would need to be taken into account. BUT if you know that the field date formats are one of these:
'yyyy-mm-dd'
'yyyy-mm-dd hh:mm:ss'
'yyyy-mm-dd whatever'
This code will help you:
SELECT count(*) FROM `table`
WHERE DATE(STR_TO_DATE(`column`, '%Y-%m-%d')) IS NOT NULL
AND `column` NOT REGEXP '^[0-9\.]+$'
Basically :
the first condition tells you if is a date, but unfortunately doesn't exclude numbers (ex: DATE(STR_TO_DATE(**1**, '%Y-%m-%d')) = '2001-00-00'
the second ensures that numbers are excluded, which leaves you with dates only that follow the formats above.
If count(*) is >0 then it's a date, if it is 0 it's something else.
Note
This method works for strings of any date format as long as you know in advance what format they follow (which I know is not always the case but still helpful). Just replace the format a priori in STR_TO_DATE
i can't understand your purpose clearly, maybe this is a idea;
SELECT DATE_FORMAT(yourFiled, '%Y-%m-%d') days FROM yourTable GROUP BY days;
this is not null; you can change it. some like
SELECT DATE_FORMAT(yourFiled, '%Y-%m-%d') days FROM yourTable WHERE yourFiled > '2013-9-23 00:00:00' GROUP By days;
Try this:
SELECT DATE(STR_TO_DATE('2013-00-30', '%Y-%m-%d')); --is also NOT NULL
Related
I have a column where a date store in ddmmyy format (e.g. 151216). How can I convert it to yyyy-mm-dd format (e.g 2016-12-15) for calculating a date difference from the current date? I try using DATE_FORMAT function but its not appropriate for this.
If you want to get the date difference, you can use to_days() after converting the string to a date using str_to_date():
select to_days(curdate()) - to_days(str_to_date(col, '%d%m%y'))
or datediff():
select datediff(curdate(), str_to_date(col, '%d%m%y'))
or timestampdiff():
select timestampdiff(day, str_to_date(col, '%d%m%y'), curdate())
You can use the function, STR_TO_DATE() for this.
STR_TO_DATE('151216', '%d%m%y')
A query would look something like:
select
foo.bar
from
foo
where
STR_TO_DATE(foo.baz, '%d%m%y') < CURDATE()
Note: Since both STR_TO_DATE() and CURDATE() return date objects, there's no reason to change the actual display format of the date. For this function, we just need to format it. If you wanted to display it in your query, you could use something like
DATE_FORMAT(STR_TO_DATE(foo.baz, '%d%m%y'), '%Y-%m-%d')
To get the difference, we can simply subtract time
select
to_days(CURDATE() - STR_TO_DATE(foo.baz, '%d%m%y')) as diff
from
foo
If you wanted to only select rows that have a difference of a specified amount, you can put the whole to_days(...) bit in your where clause.
SELECT STR_TO_DATE('151216', '%d%m%y') FROM `table`
use this '%d%m%y'
I have a column that stores dates as text, I need to select all the entries with date less than the date of today.
If I use this:
SELECT *
FROM mytab
WHERE expire < CURRENT_DATE( )
ORDER BY expire DESC
It doesn't select the correct entries but only the ones with da_expire empty.
How can I fix it?
In the first place, why are you storing it as string?
You need to convert it to date using MySQL's builtin function so you can be able to compare it with today's date.
WHERE STR_TO_DATE(expire, '%Y/%m/%d %H:%i') < CURDATE()
This will be a little slower since it will not use any index if you have one defined on the column.
MySQL Docs: STR_TO_DATE()
Use STR_TO_DATE(expire, '%m/%d/%Y') instead of expire in the query. I have assumed you are storing the date in month day year format. You will need to adjust the format as per the string format. However, for performance reasons convert the type of expire during load/insert process .
select DATE_FORMAT('8:48:30 AM', '%H:%i:%s')
It returns Null why ?
but when using
select DATE_FORMAT(CURTIME(), '%H:%i:%s')
It return formatted value.
It's returning NULL because MySQL isn't successfully parsing the string into a valid DATETIME value.
To fix the problem, use the STR_TO_DATE function to parse the string into a TIME value,
SELECT STR_TO_DATE('8:48:30 AM', '%h:%i:%s %p')
Then, to get the TIME value converted to a string in a particular format, use the TIME_FORMAT function, e.g. 24-hour clock representation:
SELECT TIME_FORMAT(STR_TO_DATE( '8:48:30 AM', '%h:%i:%s %p'),'%H:%i:%s')
returns:
--------
08:48:30
The method DATE_FORMAT is used to display date and time, however in the first you are not assigning any date except time, so its is throwing null.
From the manuals -
DATE_FORMAT Formats the date value according to the format string.
In MySql version 5.5 SELECT DATE_FORMAT( CURTIME( ) , '%H:%i:%s' ) returns null
DATE_FORMAT 's first parameter is of type DATETIME. On recent mysql server versions both your queries return NULL.
So the answer to your question is that this difference in behaviour is because of a bug in your mysql version - in some way it converts the TIME to DATETIME, while it cannot convert the string to DATETIME.
Here is also an example of a working query:
select DATE_FORMAT(NOW(), '%H:%i:%s')
NOW() returns a DATETIME while CURTIME() returns TIME.
To my knowledge, I think it's because MySQL recognises the function as a time, and therefore knows how to handle it. Whereas, in the first example, it regards it as a string and doesn't know what to do with it.
I have the following where clause
AND DATE_FORMAT( l.created_on, "%d/%m/%Y" ) BETWEEN '06/02/2013' AND '07/02/2013'
where created_on is a timestamp.
Now for some reason the query returns rows from previous months as well. anyone knows why?
NOTE :
I need the date to be in that specific format
Mysql string date format follows pattern yyyy-mm-dd. Do not convert to dates if you have timestamps, just compare the timestamps.
WHERE l.created_on
BETWEEN UNIX_TIMESTAMP('2012/02/06') AND UNIX_TIMESTAMP('2013/02/07')
if created_on is already a date (datatype),
you can directly query it using,
WHERE created_on BETWEEN '2013-02-06' AND '2013-02-07'
but if date is a string, use STR_TO_DATE
WHERE STR_TO_DATE(l.created_on, '%d-%m-%Y') BETWEEN '2013-02-06' AND '2013-02-07'
UPDATE 1
since you don't want to change the format of your inputted date, then you need to format it using STR_TO_DATE
WHERE l.created_on BETWEEN STR_TO_DATE('06/02/2013','%d/%m/%Y') AND
STR_TO_DATE('07/02/2013','%d/%m/%Y')
I want to select rows from a table given a particular date of record in mysql
SELECT * from TABLENAME WHERE FROM_DATE='06/11/2012'
I am not getting anything useful.
First of all, you should use the standard date format Y-m-d - otherwise you have to make some nasty queries and sorting is a real b*tch.
Using the standard date format you can easily do something like this:
SELECT * FROM tablename WHERE from_date > '2012-06-11'
DATE comparisons are very likely what you want here. If your from_date column has the data type of DATE, then your code should be safe and robust if you do this:
WHERE from_date = STR_TO_DATE('06/11/2012', '%m/%d/%Y')
#Repox pointed out that you might consider putting your date literals in the canonical format '2012-06-11'. That's true, if you can do it. But STR_TO_DATE will do it for you if you need it to. There's a list of the %x conversion items here. http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_date-format
If you're using DATETIME data types, beware: comparisons are more complex than they seem. DATETIME items are like floating point numbers: if one of them exactly equals another it's only by coincidence. That's because they represent moments (milliseconds) in time, not just days.
Presuming your from_date column has the DATETIME type, you should use
WHERE from_date >= STR_TO_DATE('06/11/2012', '%m/%d/%Y')
AND from_date < STR_TO_DATE('06/11/2012', '%m/%d/%Y') + INTERVAL 1 DAY
This will catch all moments in time on the day you want, up to but not including the first moment of the next day.
If your from_date items are represented as character strings, take the trouble to convert them to DATE or DATETIME data types. Seriously. Your results will be far better.
SELECT * from TABLENAME WHERE FROM_DATE='2012/06/13'
It would be better if you use the DATE() function of mysql
SELECT * FROM tablename WHERE DATE(from_date) > '2012-06-11'
Because, if the datatype of the from_date you set as TIMESTAMP or DATETIME then it won't return the correct results sometimes when you directly use the '>' symbol