I've just now started working with SQL; I need to represent some information in some tables, date and time being two of them.
I want to know, if there is a better data type to represent date and time than varchar() or numeric().
Are there any SQL primitives to represent date and time?
Yes there are date time specific data types for most SQL database implementations.
Exact syntax depends on the RDMS vendor, but here are some examples for the very popular Microsoft SQL Server and Oracle (previously Sun) MySQL.
SQL Date Functions
MySQL comes with the following data types for storing a date or a date/time value in the database:
DATE - format YYYY-MM-DD
DATETIME - format: YYYY-MM-DD HH:MM:SS
TIMESTAMP - format: YYYY-MM-DD HH:MM:SS
YEAR - format YYYY or YY
SQL Server comes with the following data types for storing a date or a date/time value in the database:
DATE - format YYYY-MM-DD
DATETIME - format: YYYY-MM-DD HH:MM:SS
SMALLDATETIME - format: YYYY-MM-DD HH:MM:SS
TIMESTAMP - format: a unique number
Or you can search for other database implementations. Ex:
"Oracle date time data type sql"
You might find:
Overview of Datetime and Interval Datatypes and Time Zone Support
It depends which flavor you're working with, but most variations of SQL offer date, smalldate, datetime, datetimeoffset, etc.
It really just depends on how you'd like to show the date, and how much information you'd like to show.
The most common form is datetime, and is explained (along with all others) at MSDN Transact-SQL
Related
I have a Oracle SQL statement where I have to get the current timestamp as one of the columns. But I dont require the Timezone which CURRENT_TIMESTAMP gives or the AM/PM given by LOCALTIMESTAMP.
I require the current timestamp in 24hr format without the timezone.
Is it possible to get that in Oracle SQL?
It seems you're mixing 2 concepts here: "datatype" and "date format mask".
data type: LOCALTIMESTAMP returns datatype TIMESTAMP and CURRENT_TIMESTAMP returns datatype TIMESTAMP WITH TIME ZONE. TIMESTAMP is similar to DATE but has a higher precision. As usual... checking the docs is worth it.
date format mask: determines how you display the date information. Americans can't read 24 hour format, the rest of the world is confused by AM/PM. Fortunately, you can decide how you want to display the date as explained in the oracle docs.
If you just want to return the current date in 24 hour format you could do something like:
SELECT
TO_CHAR(SYSDATE,'DD-MON-YYYY HH24:MI:SS') as mydate,
<other columns>
FROM
<table_name>
If you need the date to be more precise and you require fractional seconds then you can use SYSTIMESTAMP instead of DATE with a format mask 'DD-MON-YYYY HH24:MI:SS.FF9'
I have a dataset with column named "msg_dateStr" which contains user's accessing date and time.
I tried to split it into two different columns; date and time, and I did SELECT date(msg_dateStr, 'localtime') as Year
but it returns null straight.
I don't know why this happens and how I can make sure something went wrong.
Any advice will be appreciated.
The date to be used by the Date and Time Functions such as date MUST be in a format that is recognised by SQLite for a useful result. Recognised formats are (extract from the link above) :-
Time Strings
A time string can be in any of the following formats:
YYYY-MM-DD
YYYY-MM-DD HH:MM
YYYY-MM-DD HH:MM:SS
YYYY-MM-DD HH:MM:SS.SSS
YYYY-MM-DDTHH:MM
YYYY-MM-DDTHH:MM:SS
YYYY-MM-DDTHH:MM:SS.SSS
HH:MM
HH:MM:SS
HH:MM:SS.SSS
now
DDDDDDDDDD
You need to ensure that the data is saved accordingly or alternately (but not recommended at all) reformat the column via SQL (e.g. using the substr built-in function).
How to get date and time difference between 10/12/2010 07:35:02 PM and 2010-11-19 21:51:01.713. Where first date is in MM-DD-YYYY format and Second date is in YYYY-MM-DD Format Rest is time it is also in different format as first format has "pm" in it. Please let me know how to write a query in sql 08 to calculate date and time difference?
The datetime data type in SQL Server is actually a 8-byte number. It may be represented in different formats to please humans but the format has no meaning to SQL Server itself.
To calculate the time difference between to datetime values you can use the built-in DATEDIFF function, which you can find details about here: http://technet.microsoft.com/en-us/library/ms189794.aspx
This will work thanks to the SQL Server ability to parse formatted dates for us:
select datediff(day, '10/12/2010 07:35:02 PM', '2010-11-19 21:51:01.713')
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I have 2 questions:
I want to compare a field whose data type is "Date" against a given date. The DB is oracle and being a mysql guy I'm finding it difficult to come up with simple queries.
The field("date_closed") stores date in UTC format (24-Aug-2011 18:55:11 for example) and I want to convert it to PST for comparison.
I tried this query but it returns some extra rows in the data set(obviously):
select * from table1 where trunc(date_closed)=to_date('2011-08-24','yyyy-mm-dd')
How do I covert to PST format before comparison?
In the same query how do I compare "date_closed" against the current date?
You need the NEW_TIME function
Dates don't include timezone in Oracle, and are assumed to be in the database timezone (which may by UTC but probably isn't). You should look at the TIMESTAMP WITH TIMEZONE data types.
Also, bear in mind that if you are comparing to the current date - I assume that you want to strip off the timestamp and compare only the day.
So, if new_time(date_closed,'GMT','PST') translates the date , your where clause will be comparing something like
trunc(new_Time(date_closed,'GMT','PST')) = trunc(sysdate)
to get all records with date_closed on the current day in PST.
I am trying to insert a datetime value into a SQLite database. It seems to be sucsessful but when I try to retrieve the value there is an error:
<Unable to read data>
The SQL statements are:
create table myTable (name varchar(25), myDate DATETIME)
insert into myTable (name,mydate) Values ('fred','jan 1 2009 13:22:15')
The format you need is:
'2007-01-01 10:00:00'
i.e. yyyy-MM-dd HH:mm:ss
If possible, however, use a parameterised query as this frees you from worrying about the formatting details.
The way to store dates in SQLite is:
yyyy-mm-dd hh:mm:ss.xxxxxx
SQLite also has some date and time functions you can use. See SQL As Understood By SQLite, Date And Time Functions.
You have to change the format of the date string you are supplying in order to be able to insert it using the STRFTIME function. Reason being, there is no option for a month abbreviation:
%d day of month: 00
%f fractional seconds: SS.SSS
%H hour: 00-24
%j day of year: 001-366
%J Julian day number
%m month: 01-12
%M minute: 00-59
%s seconds since 1970-01-01
%S seconds: 00-59
%w day of week 0-6 with sunday==0
%W week of year: 00-53
%Y year: 0000-9999
%% %
The alternative is to format the date/time into an already accepted format:
YYYY-MM-DD
YYYY-MM-DD HH:MM
YYYY-MM-DD HH:MM:SS
YYYY-MM-DD HH:MM:SS.SSS
YYYY-MM-DDTHH:MM
YYYY-MM-DDTHH:MM:SS
YYYY-MM-DDTHH:MM:SS.SSS
HH:MM
HH:MM:SS
HH:MM:SS.SSS
now
Reference: SQLite Date & Time functions
Use CURRENT_TIMESTAMP when you need it, instead OF NOW() (which is MySQL)
Read This: 1.2 Date and Time Datatype
best data type to store date and time is:
TEXT best format is: yyyy-MM-dd HH:mm:ss
Then read this page; this is best explain about date and time in SQLite.
I hope this help you
This may not be the most popular or efficient method, but I tend to forgo strong datatypes in SQLite since they are all essentially dumped in as strings anyway.
I've written a thin C# wrapper around the SQLite library before (when using SQLite with C#, of course) to handle insertions and extractions to and from SQLite as if I were dealing with DateTime objects.