问题
I am seeeing my dates are stored in database in this format for a column (datetime datatype) 2011-01-14 10:15:41.787 i.e YYYY-MM-DD way . How could I make the default storage in YYYY-DD-MM format . Do I need to set that for all the DBS, or I can set it for single DB and how ?
回答1:
I have the column in datetime datatype, right now it is saving as 2011-01-14 10:15:41.787 , my question is how can I set the db to store it as 2011-14-01 10:15:41.787
That is the crux of the confusion. Just because SQL Server Management Studio displays a datetime column in that format does not mean that it is stored AS TEXT YYYY-MM-DD hh:mm:ss.zzz. It is stored as binary, something like 0000101000001010..
Your dates are stored in SQL Server as a series of bytes (bits really) that make up some numeric value that is an offset from 1900-01-01. There is no inherent format the the dates. What you are referring to is that SSMS by default shows [display] datetime columns as YYYY-MM-DD hh:mm:ss.zzz. If you use a front-end programming tool, that too may impose a default [display] format unless you have asked for another one.
There is absolutely NO way to make SSMS show datetime data in another format through options or configuration. If you must, you would have to update the SQL query to convert the datetime column to a VARCHAR column containing the TEXTual equivalent in a particular format. That may be useful in SSMS, but would be bad when used as a data source to front-end GUI/web apps - since the values are not datetime and cannot be used for interval calculation, graphing, bound to date controls etc.
See this example of displaying time (getdate()) as YYYY-DD-MM, a very unusual format. Notice the date field/variable has to be used twice:
select stuff(convert(char(7), getdate(), 120), 5, 0, '-' + convert(char(2), getdate(), 3))
回答2:
DATETIMEs are stored internally as two 4 byte integers, so firstly you are seeing a formatted representation for the UI - it's not actually stored in a particular date/time format as such. e.g. if you insert just a date like "2010-01-01" then it will still hold the time element: 2010-01-01 00:00:00.000
If you're only interested in the DATE part, then you can format the DATETIME for output either in your front-end code or via your query:
e.g.
SELECT CONVERT(VARCHAR(8), GETDATE(), 121)
So even if the DATEs you insert contain a time, that will be ignored when returned. You could also ensure you only insert dates without the time specified - you need to handle that in whatever code is doing the INSERTs. e.g. from .NET, instead of passing in DateTime.Now you could pass in DateTime.Now.Date.
In SQL Server 2008, there is a DATE datatype which is there to only store a DATE (without time) which is really what you want in this kind of scenario.
来源：https://stackoverflow.com/questions/4711719/change-default-dateformat-stored-in-a-database