I need to know the week of year of a timestamp using Derby/JavaDB. And to make it worse I have to extract it from a parameter not a column. Don't ask why but that should be a minor problem.
On DB2 I say someting like
VALUES WEEK_ISO(?)
But how do I get the same result with Derby aka JavaDB?
Thanks Bryan, your Link was very helpful.
http://therealdanvega.com/blog/2010/02/17/creating-apache-derby-custom-functions-part-2
It seems there is no week function in derby but it is very easy to program such a function yourself. Especially when you use it from Java.
Related
Long time listener, first time caller.
At work we have all of the date columns for most tables stored in as a simple "string" (varchar) formats. Such as yyyymmdd (eg. 20220625) or yyyymm (202206) etc.
Now for a lot of queries that are time based we need to compare to current date, or some fixed offset from current date.
Now two obvious versions that I know of to get current utc date into either of those formats are the following (for yyyymm as example):
SELECT LEFT(CONVERT(VARCHAR, GETUTCDATE(), 112), 6) ...
SELECT CONVERT(VARCHAR(6), GETUTCDATE(), 112) ...
I'm wondering if anyone knows of a better way, either both idiomatically or performance wise to convert those, and/or is there anything wrong with the second one to be worried about versus the first one in regards to either security/reliability etc? The second one definitely satisfies my code golf sensibilities, but not if it's at the expense of something I'm unaware of.
Also for some extra context the majority of our code runs in SQL Server or T-SQL, BUT we also need to attempt to be as platform agnostic as possible as there are customers on Oracle and/or Mysql.
Any insight/help would be highly appreciated.
There is no problem with either approach. Both work just fine. It is a matter of personal preference which to choose. The first looks more explicit, the second is shorter and thus easier to read maybe. As to performance: You want to get the current day or month only once in a query, so the call doesn't realy affect query runtime.
As to getting this platform agnostic is quite a different story. SQL dialects differ. Especially when it comes to date/time handling. You already notice that SQL Server's date functions are quite restricted. In Oracle and MySQL you would simple state the format you want (TO_CHAR(SYSDATE, 'YYYYMM') in Oracle and DATE_FORMAT(CURRENT_DATE, '%Y%m') in MySQL). But you also see that the function calls differ.
Now, you could write a user defined function GET_CURRENT_MONTH_FORMATTED for this which would return the string for the current month, e.g. '202206'. Then you'd have the different codes hidden in that function and the SQL queries would all look the same. The problem, though, is how to tell the DBMS that the function result is deterministic for a particular timestamp? If you run the query on December 31, 2022 at 23:50 and it runs until January 1, 2023 at 0:20, you want the DBMS to call this function only once for the query resulting in '202212' and not being called again, suddenly resulting in another string '202301'. I don't even know whether this is possible. I guess it is not.
I think you cannot write a query that does what you want and looks the same in all mentioned DBMS.
Just learning SQL and I've searched many options about converting a DateTime into a Date, and I do not want current date. It's a super simple query from this website: https://sqlzoo.net/wiki/Guest_House_Assessment_Easy
SELECT booking_date, nights
FROM booking
WHERE guest_id=1183
But the output is with the timestamp and I just want the date. I've searched so many forums and tried all their suggestions, including this:
SELECT CONVERT(varchar(10), <col>, 101)
So I've done:
SELECT CONVERT(varchar(10), booking_date,101), nights
FROM booking
WHERE guest_id=1183
But I'm getting syntax errors. This is probably so simple and you'll all think me an idiot, but I'd greatly appreciate help. It's driving me nuts.
When I fiddled about at your sqlzoo link I got the error
execute command denied to user 'scott'#'localhost' for routine 'gisq.to_date'`.
When I googled gisq.to_date I got this link https://sqlzoo.net/wiki/Format_a_date_and_time
Which has examples of how this dialect represents dates. See if you can work it out. Something like this:
SELECT date_format(booking_date,'%d/%m/%Y')
FROM booking
You didn't post the error in your question which is a big mistake. When you get an error message, you actually have something to work from.
It is also very important to note that the query above returns a string, not a date. It's only good for display, not for date arithmetic
TBH that seems like a terrible site to learn on as it gives no clues about the dialect. it looks like Oracle but to_date and trunc don't work.
The use of convert() suggests that you think you are uinsg SQL Server. If you only want the date component of a date/time data type, then you can use:
SELECT CONVERT(DATE, booking_date), nights
FROM booking
WHERE guest_id = 1183;
The syntax error suggests that you are not using SQL Server.
CONVERT() is bespoke syntax for SQL Server. Examples of similar functionality in other databases are:
DATE(booking_date)
TRUNC(booking_date)
DATE_TRUNC('day', booking_date)
In addition, what you see also depends on the user-interface.
In your case, the data is being stored as a date with no time component, but the UI is showing the time. For that, you want to convert to a string. That site uses MariaDB -- which is really a flavor of MySQL-- and you would use:
DATE_FORMAT(booking_date, '%Y-%m-%d')
I am running queries on an alarm system signal automation platform database in SQL Server 2012 Management Studio, and I am running into some hiccups.
My queries run just fine, but I am unable to refine my results to the level that I would like.
I am selecting some columns that are formatted as DATETIME, and I simply want to take the value in the column and subtract 4 hours from it (i.e., from GMT to EST) and then output that value into the query results.
All of the documentation I can find regarding DATESUB() or similar commands are showing examples with a specific DATETIME in the syntax, and I don't have anything specific, just 138,000 rows with columns I want to adjust time zones for.
Am I missing something big or will I just need to continue to adjust manually after I being manipulating my query result? Also, in case it makes a difference, I have a read-only access level, and am not interested in altering table data in any way.
Well, for starters, you need to know that you aren't restricted to use functions only on static values, you can use them on columns.
It seems that what you want is simply:
SELECT DATEADD(HOUR,-4,YourColumnWithDateTimes)
FROM dbo.YourTable
Maybe it will be helpful
SELECT DATEPART(HOUR, GETDATE());
DATEPART docs from MSDN
I have what I thought was a simple task: create a Measure that returns the distinct count of a field for all records that meet a specific filter condition, in this case a date filter. I came up with the following:
=CALCULATE(DISTINCTCOUNT(ExitFilter[Dim_Client_ID]),ExitFilter[ExitDate]<1/1/2014)
and the result was (blank) so I tried:
=CALCULATE(DISTINCTCOUNT(ExitFilter[Dim_Client_ID]),FILTER(ExitFilter,ExitFilter[ExitDate]<1/1/2014))
and the result was still (blank) so I tried:
=CALCULATE(COUNTROWS(DISTINCT(ExitFilter[Dim_Client_ID])),FILTER(ExitFilter,ExitFilter[ExitDate]<1/1/2014))
and the result was still (blank). What am I missing? And what does (blank) signify?
If it's not clear 'ExitFilter' is a table, [Dim_Client_Id] is a column, and [ExitDate] is a date column.
Tom, comparing dates is from my experience best done with simple Date function.
So if you update your formula to something like this:
=CALCULATE([Your Measure], Table[DateColumn]>DATE(2014,1,1))
You will get what you need with easy-to-read code. Also, for any advanced time-based calculations, the best way to go is creating dates table and using Time Intelligence module of PowerPivot.
Tom, think your second attempt is 'right' but you need to be careful about how you are expressing the date.
Later versions PowerPivot are a little bit funny about this and while "01/01/2014" should work I don't think it will.
Instead try replacing 01/01/2014 with 41640 - this is is the underlying date value, its hacky but then so is any kind of hard coded date :-)
I don't have much experience so I apologize in advance for a potentially dumb question. I did not create these tables nor the queries that have been used in the past. With that said --
For the past several months I have been using a date conversion query that was given to me to update columns from an integer to a date. It used to work just fine and I swear everything is the same for my latest data extractions, but at some point the dates started getting wonky. For example, a typical date column might look like:
58222
58158
59076
58103
And the conversion query looks something like this:
IIf([D_posting]<>0,[D_posting]-18261,0)
And returns the above dates as:
05/27/2059
03/24/2059
09/27/2061
01/28/2059
Which obviously is wrong. The situation kind of reminds me of how I remember we generated random numbers in C++ (which was a long time ago), but for the life of me I can't figure out how to reverse engineer the correct subtraction factor without a reference point.
I also tried using the CDate() function instead, and it resulted in a bunch of future dates also, leading me to wonder if there's something else wrong. I work for a small physicians group so it might be something in the Electronic Health Records software, but I'd like suggestion on what I should check to make sure it's nothing that I've done.
You could create a query that uses the 'cdate' function (see below) to return the date. You can modify the code so that it subtracts the offset (maybe 18261?)
In the immediate window of VBA you can tinker with the following:
The 'cdate' will take a number and convert it to a date:
?cdate(41925)
10/13/2014
The 'cdbl' will take a date and convert to a number.
?CDbl(Date())
41926