What is the fastest way to get only time part of datetime - sql-server

My problem is that we are using Datetime column in our database but we need to show our date in different calendar like Hijri or Shamsi With the Time.
So with complex query cost of conversion is very high and i need an efficient way to get Time and concatenate it with the converted date part.
Right now i am using these approaches
1-
CONCAT(dbo.getShamsiDate( JI.Job_start_execution_date ),' ',FORMAT(JI.Job_start_execution_date,'HH:mm:s')) AS [JobStart]
JobStart
1399/05/13 19:25:47
2-
SELECT CONVERT(VARCHAR(10), #Job_start_execution_date , 108) JobStart;
JobStart
----------
14:43:35
My question is this:
Which one is faster or be suited and is there any faster way?

Just cast/convert it to a time, as that retain the correct typing (it's still a date and time data type):
SELECT CONVERT(time(0),datetimevalue), CAST(datetimevalue AS time(3))
As the value is a datetime, the value will be accurate to 1/300th of a second, however, choose a precision appropriate for your data.

Related

How to use wildcard for datetime filed

How do I use wildcards for datetme? SubmitDate field is a datetime but the query that I tried returns something totally different. I want records where submitDate begins with 2019-08
This is the code I've tried:
select *
from INVPol
where SubmitDate like '[2019-08]%'
"How do I use wildcards for datetme" Quite simply, you don't. Use proper date logic. For what you have the best way would be the below
SELECT *
FROM dbo.INCPol
WHERE SubmitDate >= '20190801'
AND SubmitDate < '20190901';
Using a lower boundary with a greater or equal to, and an upper boundary with a less than will mean that every row with a date in August 2019 will be returned. This is generally seen as a the "best" way as it's the most encompassing. Logic using BETWEEN can give incorrect results when using values with a time portion. That's because 2019-08-31T00:00:00.0000001 is not BETWEEN '20190801' and '20190831' (it's 1/1000000 of a second after the end threshold); this would mean you would effective lose a days worth of values. Also the date '2019-09-01T00:00:00.0000000' is BETWEEN '20190801' AND '20190901', so you could get (some) unwanted rows.
Trying to use a wildcard on a date would mean you would have to convert the value of the column to a varchar, which will cause performance issues. Leave the date as a date and time datatype and query it as one.

Extract data by day from SQL Server

I need to get all the values from a SQL Server database by day (24 hours). I have timestamps column in TestAllData table and I want to select the data which only corresponds to a specific day.
For instance, there are timestamps of DateTime type like '2019-03-19 12:26:03.002', '2019-03-19 17:31:09.024' and '2019-04-10 14:45:12.015' so I want to load the data for the day 2019-03-19 and separately for the day 2019-04-10. Basically, it is needed to get DateTime values with the same date.
Is this possible to use some functions like DatePart or DateDiff for that?
And how can I solve such problem overall?
As in this case, I do not know the exact difference in hours between a timestamp and the end of the day (because there are various timestamps for 1 day) and I need to extract the day itself from the timestamp. After that, I need to group the data by days or something like this and get block by block. For example:
'2019-03-19' - 1200 records
'2019-04-10' - 3500 records
'2019-05-12' - 10000 records and so on
I'm looking for a more generic solution not supplying a timestamp (like '2019-03-19') as a boundary or in a where clause because the problem is not about simply filtering the data by some date!!
UPDATE: In my dataset, I have about 1,000,000 records and more than 100 unique dates. I was thinking about extracting the set of unique dates and then kind of run a query in the loop where the data would be filtered by the provided day. It would look in such a way:
select * from TestAllData where dayColumn = '2019-03-19'
select * from TestAllData where dayColumn = '2019-04-10'
select * from TestAllData where dayColumn = '2019-05-12'
...
I might use this query in my code, so I may run it in the loop from Scala function. However, I am not sure that in terms of performance it would be ok to run separate unique dates extraction query.
Depending on whether you want to be able to work with all the dates (rather than just a subset), one of the easiest ways to achieve this is with a cast:
;with cte as (SELECT cast(my_datetime as date) as my_date, * from TestAllData)
SELECT * FROM cte where my_date = '2019-02-14'
Note when casting datetime to date, times are truncated, ie just the date part is extracted.
As I say though, whether this is efficient, depends on your needs, as all datetime values from all records will be cast to date, before the data is filtered. If you want to select several dates (as opposed to just one or two), however, it may prove overall quicker, as it reads the whole table once and then gives you a column upon which you can much more efficiently filter.
If this is a permanent requirement, though, I would probably use a persisted computed column, which effectively would mean that the casting is done once initially and then only again if the corresponding value changed. For a large table I would also strongly consider an index on the computed column.

EPOCH timestamp from SQL Server

I feel like I've read a ton of these corresponding posts such as,
converting Epoch timestamp to sql server(human readable format)
& How do I convert a SQL server timestamp to an epoch timestamp?
But can't seem to get my particular use-case working. I need to convert an epoch timestamp to a normal date/time value. Currently, the column is a nvarchar(max) type. Here's an example of one of the dates:
1478563200000
I'm trying to get it to look like the following:
2019-01-14 00:00:00.0000000
I've tried the following to no success all with the same error message:
select DATEADD(SS, CONVERT(BIGINT, baddate), '19700101') as gooddate
from table
"Arithmatic overflow error converting expression to data type int"
I've tried minutes, seconds, days, all same error message and at this point I'm about to tell the guys to send the data in a different format.
Try
select DATEADD(SS, CONVERT(INT, CONVERT(BIGINT, baddate)/1000), '19700101') as gooddate
from table
DATEADD expects an int, not a bigint. Since your timestamp is in milliseconds, it won't "fit" in an int. If you trade-in millisecond resolution for second resolution by dividing by 1000 it will fit in an integer and make DATEADD happy. So first we convert the NVARCHAR to BIGINT (why store as NVARCHAR in the first place?), then divide by 1000 and then convert to INT.
Another option is to divide the value by 1000 at the time of insert (and, again, make the column an int in the first place). That'll save a lot of CONVERTs everywhere (you can get rid of them all) and probably speed up your queries quite nicely. Then again, you could even convert the column to datetime (or datetime2 or whatever type is best suited) and leave out the entire dateadd/convert mess in your queries alltogether. Always try to get your data ad close to the final datatype you need it in later.
Edit: I just realized you can probably leave one convert out:
select DATEADD(SS, CONVERT(BIGINT, baddate)/1000, '19700101') as gooddate
from table
This is the same as the original suggestion, only this time the cast to int is implicit. But converting your data upon insert is still probably the better idea. So the rest of my post still stands.
You can get the correct result to the millisecond, that works with years 0001 through 9999, using the accepted answer
here.
declare #x nvarchar(max) = N'1478563200000'
select dbo.UnixTimeToDateTime2(#x)

SqlDateTime overflow Exception

I am trying to insert a time only value, but get the following error
ex {"SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM."} System.Exception
From the front end, the time is selected using the "TimeEdit" control, with the up and down arrows. The table in SQL Server has the fields set as smalldatetime. I only need to store the time. I use the following to return data to the app
select id,CONVERT(CHAR(5),timeFrom,8)as timeFrom,CONVERT(CHAR(5),timeTo,8)as timeTo
FROM dbo.Availability
where id = #id
and dayName = #weekday
How do I pass time only to the table?
Edit ~ Solution
As per Euardo and Chris, my solution was to pass a datetime string instead of a time only string. I formatted my result as per Time Format using "g".
Thanks
You can set the date to 1/1/1753 wich is date min value for datetime in MSSQL and then add the hour you want to store. Of course you have to consider this every time you need to get the value, but you can wrap that with some helpers.
Or you can use MSSQL 2008 and use the new TIME datatype.
Pick a date that is in the range(ie, 1/1/1970) and use it for everything you insert.
If you are only keeping track of the time, think about storing it in an int as an offset from midnight in whatever granualarity you need (seconds, minutes, hours, ...). You can then convert it to a TimeSpan in your code using the appropriate TimeSpan.From??() method. To go back the other way, you can use TimeSpan.Total?? and truncate if need be. If you need to do manual queries you can write a SQL function that will convert hours/mins/seconds to the equivalent offset.
I prefer this over using a datetime and picking an arbitrary day as it makes the purpose of the field clearer, which reduces confusion.
there is no such thing as Time in SQL, there is only DateTime.
For your purpose, I would use something like this to only return the time portion.
SELECT (GETDATE() - (CAST(FLOOR(CAST(GETDATE() as FLOAT)) AS DateTime)))
where GETDATE() is the datetime you want to filter.
When setting the time in the database, you will have to add '01/01/1901' or '01/01/1753' to the time.
Dont use CAST and Convert to varchar when working with datetime, its slow. Stick to floating numerical operations.

SQL Server DateTime conversion failure

I have a large table with 1 million+ records. Unfortunately, the person who created the table decided to put dates in a varchar(50) field.
I need to do a simple date comparison -
datediff(dd, convert(datetime, lastUpdate, 100), getDate()) < 31
But it fails on the convert():
Conversion failed when converting datetime from character string.
Apparently there is something in that field it doesn't like, and since there are so many records, I can't tell just by looking at it. How can I properly sanitize the entire date field so it does not fail on the convert()? Here is what I have now:
select count(*)
from MyTable
where
isdate(lastUpdate) > 0
and datediff(dd, convert(datetime, lastUpdate, 100), getDate()) < 31
#SQLMenace
I'm not concerned about performance in this case. This is going to be a one time query. Changing the table to a datetime field is not an option.
#Jon Limjap
I've tried adding the third argument, and it makes no difference.
#SQLMenace
The problem is most likely how the data is stored, there are only two safe formats; ISO YYYYMMDD; ISO 8601 yyyy-mm-dd Thh:mm:ss:mmm (no spaces)
Wouldn't the isdate() check take care of this?
I don't have a need for 100% accuracy. I just want to get most of the records that are from the last 30 days.
#SQLMenace
select isdate('20080131') -- returns 1
select isdate('01312008') -- returns 0
#Brian Schkerke
Place the CASE and ISDATE inside the CONVERT() function.
Thanks! That did it.
Place the CASE and ISDATE inside the CONVERT() function.
SELECT COUNT(*) FROM MyTable
WHERE
DATEDIFF(dd, CONVERT(DATETIME, CASE IsDate(lastUpdate)
WHEN 1 THEN lastUpdate
ELSE '12-30-1899'
END), GetDate()) < 31
Replace '12-30-1899' with the default date of your choice.
How about writing a cursor to loop through the contents, attempting the cast for each entry?When an error occurs, output the primary key or other identifying details for the problem record.
I can't think of a set-based way to do this.
Not totally setbased but if only 3 rows out of 1 million are bad it will save you a lot of time
select * into BadDates
from Yourtable
where isdate(lastUpdate) = 0
select * into GoodDates
from Yourtable
where isdate(lastUpdate) = 1
then just look at the BadDates table and fix that
The ISDATE() would take care of the rows which were not formatted properly if it were indeed being executed first. However, if you look at the execution plan you'll probably find that the DATEDIFF predicate is being applied first - thus the cause of your pain.
If you're using SQL Server Management Studio hit CTRL+L to view the estimated execution plan for a particular query.
Remember, SQL isn't a procedural language and short circuiting logic may work, but only if you're careful in how you apply it.
How about writing a cursor to loop through the contents, attempting the cast for each entry?
When an error occurs, output the primary key or other identifying details for the problem record.
I can't think of a set-based way to do this.
Edit - ah yes, I forgot about ISDATE(). Definitely a better approach than using a cursor. +1 to SQLMenace.
In your convert call, you need to specify a third style parameter, e.g., the format of the datetimes that are stored as varchar, as specified in this document: CAST and CONVERT (T-SQL)
Print out the records. Give the hardcopy to the idiot who decided to use a varchar(50) and ask them to find the problem record.
Next time they might just see the point of choosing an appropriate data type.
The problem is most likely how the data is stored, there are only two safe formats
ISO YYYYMMDD
ISO 8601 yyyy-mm-dd Thh:mm:ss:mmm(no spaces)
these will work no matter what your language is.
You might need to do a SET DATEFORMAT YMD (or whatever the data is stored as) to make it work
Wouldn't the isdate() check take care of this?
Run this to see what happens
select isdate('20080131')
select isdate('01312008')
I am sure that changing the table/column might not be an option due to any legacy system requirements, but have you thought about creating a view which has the date conversion logic built in, if you are using a more recent version of sql, then you can possibly even use an indexed view?
I would suggest cleaning up the mess and changing the column to a datetime because doing stuff like this
WHERE datediff(dd, convert(datetime, lastUpdate), getDate()) < 31
cannot use an index and it will be many times slower than if you had a datetime colum,n and did
where lastUpdate > getDate() -31
You also need to take into account hours and seconds of course

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