I'm new to the SQL world and im going crazy trying to figure out how to SELECT date from a datetime field in SQLITE.
Example: value <11/11/2005 14:56>, i just want to select <11/11/2005> for EVERY ROW.
I tried strftime(), date(), CAST() and other functions but the output its always NULL.
For example i tried querying SELECT strftime('%d/%m/%Y' , columnname) AS date FROM tablename;
OUTPUT: "NULL" in every row
Can someone help me understand what im doing wrong and how can i fix it? Thank you!!!
It always returns NULL because MM/DD/YYYY is not a valid sqlite date format. Treat the column as a string and use substr and instr to drop off the time portion. Something like (no guarantees, check the doc!)
SELECT substr(columname,0,instr(columnname,' '))
Re comment "how to order by the date in descending order"
This problem is a good argument (the best argument?) for storing the date in a sqlite date/time format. There is a strategy in this post for converting MM/DD/YYYY to YYYY-MM-DD (which sorts dates correctly).
If it's not too late, it would be advisable to change the date storage to a valid sqlite date format. strftime can be used to present the date as desired, and sorting will be accurate.
Related
I am using SQLite.
In my database, I have a integer column value like 20050819. I would like to convert this as date column as like 2005-08-19.
I can achieve my requirement when using the function CONVERT(columnName, DATETIME) in MySQL server. But I need the same result in SQLite.
Is this possible in SQLite query?
You basically have to break apart the date:
select printf('%4d-%02.2d-%02.2d',
columnname/10000, columnname%10000/100, columnname%100)
from tablename;
P.S.
If you have the choice, you will be far better off storing the date in ISO standard format ('YYYY-MM-DD') in the database in the first place.
I am working on a SQLite Database which contains a column which stores value in format yyyy-MM-dd HH:mm:ss. Now I need to create a filter to select rows with filter as this datetime column.
Query:
Select * from tbl_locations where datetime >= '2013-09-11 00:00:00' and datetime <='2013-09-13 00:00:00'
Above query is returning null set despite containing values in this slot(which I verified using select statement without filter.)
Any suggestion how can i get the required data set?
Perhaps this excerpt from the SQLite documentation will help you:
1.2 Date and Time Datatype
SQLite does not have a storage class set aside for storing dates and/or times. Instead, the built-in Date And Time Functions of SQLite are capable of storing dates and times as TEXT, REAL, or INTEGER values:
TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS").
REAL as Julian day numbers, the number of days since noon in Greenwich on November 24, 4714 B.C. according to the proleptic Gregorian calendar.
INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.
Applications can chose to store dates and times in any of these formats and freely convert between formats using the built-in date and time functions.
The date and time functions that you can use in your SQL to build your query are documented at http://www.sqlite.org/lang_datefunc.html
Ok, I tested this out in MySQL but hopefully it will work. I had a table that used timestamps, and changed the column to be of type text. Then I tried the following SQL query and got the same results that I normally would (besides trailing decimals)
SELECT timestamp(stock_quote_timestamp)
FROM stock.stock_quote
WHERE stock_quote_timestamp < timestamp('2013-10-07 11:05:30')##high_date
AND stock_quote_timestamp > timestamp('2013-10-03 14:09:03');##low_date;
So basically, just convert your text statements to timestamps so that they compare correctly. Oh, and you'll also need to state what else you're SELECTing, or you could do a compound select statement: SELECT *, timestamp(stock_quote_timestamp)...
I cannot seem to figure out why datetime does not work for me on some data I imported from CSV. I have a column, TIMESTAMP, which is of type datetime.
Select TIMESTAMP from GPS limit 1 <-This gives me a time, "6/29/2009 00:00:00"
Select datetime(TIMESTAMP) from GPS limit 1 <- This gives me a pink field in SQLite manager, which seems empty.
Select datetime('now') from GPS limit 1 <- This gives me the current date and time. ("2012-12-19 20:45:17") It is formatted differently than my other data - is there a datatype issue?
What is going on? Did my "Timestamp" data not actually get converted into a DATETIME object? Why is it stored as text? Is there a way to fix this?
SQLite does not have a native date/time type; dates are stored either as numbers or as strings.
To be understood by SQLite's built-in date functions, date strings must have a format like yyyy-mm-dd hh:mm:ss.
The following code, d has the current date. Depending on the current locale, it will return a date.
Dim d As Date = Date.Today
Note: I don't want to check whether the date is valid or not, but rather to know, whether it is in a 'dd-MM-yyyy', 'MM-dd-yyyy' or any other date format..
EDIT (29/06/2012 - Friday):
The reason I am asking this question is because I am sick of trying to deal with dates in ASP.NET. I build a project on my local PC, where dates are "dd/MM/yyyy" and as soon as I upload it to the production server (usually in US, hence MM/dd/yyyy) the code breaks.
So I usually deal with dates by converting them into yyyyMMdd format and also keep them in the database like that. That is the closest I get to an exception-free coding.
In this case, it makes sense that there is no way to get the format from a returned date string. Therefore, I will carry on with my approach.
Date.Today is a DateTime, not a string. Thus, it does not have an inherent format.
It will return a Date, which I believe is a VB alias for DateTime. (If it's not, just use DateTime explicitly to be idiomatically .NET rather than using the legacy VB types.)
A DateTime value itself doesn't have a format, any more than an int is in decimal or hex. It's only when you convert the value to a string that a format is applied, and then it depends on how you convert it to a string. You shouldn't use a string conversion until you really need to, and then you should control the format so that it works the way you want it to.
As far as possible, convert text data into its "natural" type as early as possible, and keep it in that type for as long as possible. For example, avoid converting to strings when passing values in SQL queries - instead, use parameterized SQL where you can specify the parameter value as a DateTime.
What you want to know is found in:
CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern
This is the format string that will be used when you call
d.ToShortDateString()
You need to be TOLD; there's no other way. Take for example:
6/12/2012
It's valid in dd/mm/yyyy or mm/dd/yyyy format
Which one do you pick if you don't know the locale/format beforehand?
Date values don't have an intrinsic format. In other words, you can format the date to any string representation you need but the opposite conversion from a string back to a Date value requires that you know in which format you are receiving this date string.
My table contains Birthdate field which has datatype as datetime.
I want to get all records having birthday today.
How can I get it?
Try this query:
SELECT * FROM mytable
WHERE strftime('%m-%d', 'now') = strftime('%m-%d', birthday)
Having a special datetime type has always seemed like unnecessary overhead to me, integers are fast, flexible, and use less space.
For general datetime values use Unix Epoch timestamps. Easy to work with, extremely flexible, as well as timezone (and even calender!) agnostic. (I recently wrote an article on using them, which I really have to plug...)
That said, if you're only interested in dates in the Gregorian calendar you may want to use a large integer in the following format: YYYYMMDD, eg 19761203. For you particular usage you could even create a four digit integer like MMDD, say 1703 — that's got to result in fast selects!
SQLite has very poor support for storing dates. You can use the method suggested by Nick D above but bear in mind that this query will result in full table scan since dates are not indexed correctly in SQLite (actually SQLite does not support dates as a built-in type at all).
If you really want to do a fast query then you'll have to add a separate (integral) column for storing the birth day (1-31) and attach an index for it in the database.
If you only want to compare dates then you can add a single (INTEGER) column that will store the date UTC value (but this trick won't allow you to search for individual date components easily).
Good Luck