My apologies in advance for the basic (and probably silly) question.
I'm doing a SELECT query where I'm joining several tables. I have a table that contains a numeric value associated with certain days. What I would like to have in my output is the numeric value attached to today, but I'm clueless as to how to make this happen. Obviously, I would have the same value for every record in my output and I'm fine with that.
Is this even possible? If so, what would an example of the code be?
The table from which I would like the numeric value simply has dates in one column ([Calendar_Day]) and integers in another column ([X_Value]).
Below, you can see the last three lines of my SELECT statement. This latest attempt yielded NULL.
,[EnterpriseDB].[pcc].[conditions].Internal
,GETDATE() AS Date_Today
,(SELECT [X_Value] FROM [Analytics].[WorkArea].[Days_Vals] WHERE [Calendar_Day] = GETDATE()) AS BizVal_Today
Just guessing:
[Calendar_Day] is of the type date. While getdate() returns a datetime. That means the DBMS upcasts [Calendar_Day] to a datetime with a time of 00:00:00.0 in order to be able to compare the operands. But getdate() includes the current time. So unless you're executing the query at exactly 00:00:00.0 the values won't match and the subquery returns null.
To fix that, downcast getdate().
... WHERE [Calendar_Day] = convert(date, getdate()) ...
If [Calendar_Day] is also a datetime but you don't want to compare the hour (, minute, second ...) portion of it, downcast it as well.
... WHERE convert(date, [Calendar_Day]) = convert(date, getdate()) ...
Might throw any indexes out of the window though, if there are some on [Calendar_Day]. You might want to consider changing the data type to date or using a persistent, indexed computed column and compare against that, if that leads to any performance issues.
Related
Hi it is NOT my first time the i use this query:
SELECT COUNT(*) from dbo.SchDetail WHERE dbSchDate = '08-06-2020'
Query is working but he counts everytime 0.
But if i do a between "08-06-2020" and "07-06-2020".
I got the right result.
For mysql both query working fine.
But not on MSSQL.
I dont know what I do wrong.
Thanks for help
You are getting 0 because the WHERE clause filters out all rows. There are multiple reasons; for instance:
The table could be empty.
dbSchDate could be a datetime with a time component.
The constant may not be interpreted correctly as a date/time.
No values in the table might match.
I would suggest a proper date format, in YYYYMMDD format:
WHERE dbSchDate = '20200806'
You can also use:
WHERE dbSchDate >= '20200806'
dbSchDate < '20200807'
This version works even if there is a time component, as does:
WHERE CONVERT(DATE, dbSchDate) = '20200806'
There is this strange error in sql query.
The query is something like this.
select * from student where dob between '20150820' and '20150828'
But in the database the column of dob is varchar(14) and is in yyyyMMddhhmmss format,Say my data in the row is (20150827142545).If i fire the above query it should not retrive any rows as i have mentioned yyyyMMdd format in the query.But it retrives the row with yesterday date (i.e 20150827112535) and it cannot get the records with today's date (i.e 20150828144532)
Why is this happening??
Thanks for the help in advance
You can try like this:
select * from student
where convert(date,LEFT(dob,8)) between
convert(date'20150820') and convert(date,'20150828'))
Also as others have commented you need to store your date as Date instead of varchar to avoid such problems in future.
As already mentioned you would need to use the correct date type to have between behave properly.
select *
from student
where convert(date,LEFT(dob,8)) between '20150820' and '20150828'
Sidenote: You don't have to explicitly convert your two dates from text as this will be done implicitly as long as you use an unambiguous date representation, i.e. the ISO standard 'YYYYMMDD' or 'YYYY-MM-DD'. Of course if you're holding the values in variables then use date | datetime datatype
declare #startdate date
declare #enddate date
select *
from student
where convert(date,LEFT(dob,8)) between #startdate and #enddate
Sidenote 2: Performing the functions on your table dob column would prevent any indexes on that column from being used to their full potential in your execution plan and may result in slower execution, if you can, define the correct data type for the table dob column or use a persistent computed column or materialised view if your performance is a real issue.
Sidenote 3: If you need to maintain the time portion in your data i.e. date and time of birth, use the following to ensure all records are captured;
select *
from student
where
convert(date,LEFT(dob,8)) >= '20150820'
and convert(date,LEFT(dob,8)) < dateadd(d,1,'20150828')
All you have to do is to convert first the string to date.
select *
from student
where dob between convert(date, '20150820') and convert(date, '20150828')
Why is this happening?
The comparison is executed from left to right and the order of characters is determined by the codepage in use.
Sort Order
Sort order specifies the way that data values are sorted, affecting
the results of data comparison. The sorting of data is accomplished
through collations, and it can be optimized using indexes.
https://msdn.microsoft.com/en-us/library/ms143726.aspx
There are problems with between in T-SQL.
But if you want a fast answer convert to date first and use >= <= or even datediff to compare - maybe write a between function yourself if you want the easy use like between and no care about begin and start times ...
What do BETWEEN and the devil have in common?
I am trying to update my SQL DB when the the date has expired (i.e is less than now)
I have this lovely bit of SQL code
Update Notifications
SET Active = 'N'
where CAST(SetDate AS DATE) <= CAST('2012-08-23 11:19:00 +0000' AS DATE)
But it updates all the records (even if the date is not less than now)
I have also tried
Update Notifications
SET Active = 'N'
where CAST(SetDate AS DATE) < CAST('2012-08-23 11:19:00 +0000' AS DATE)
But this dosent affect any rows.
I guess I have something a little confused??
Any help???
Thanks
I cannot see anything odd about the code, except for this line:
CAST('2012-08-23 11:19:00 +0000' AS DATE)
If you are using CAST() to change it to the date, then there is no need to pass in the time portion of the value.
You did not provide the full table schema but one thing to consider is using a bit field for the Y/N values.
Here is a SQL Fiddle with the code working
Update Notifications
SET Active = 'N'
where CAST(SetDate AS DATE) <= CAST('2012-08-23' AS DATE)
One thing you have confused is types in SQL. I don't know what database you are using, but it probably has types for boolean (or int) and date. Storing booleans and dates as strings is very inefficient. For example, even if your example did work it would have to scan the entire database and cast each value in order to compare it.
The clue to the error is the < vs <=. This hints at the values being equal. If the cast fails on both sides, and returns the default value of zero, then then will be equal.
You should change your schema to use the correct types, then your query will work.
In a SQL Server table, I have a field named Timestamp, which is a 'datetime' field. On a screen I have created, a user will pass in a date (no time), and I need to return all the records for that date.
Just doing Timestamp = #Date doesn't seem to work unless the time in the field is 00:00:00. What is the most efficient way of doing this?
Since you're on SQL Server 2008, you can use the DATE datatype.
Do a comparison between
CAST(Timestamp AS DATE) = #Date
That should work and look just at the date - no time portion.
In general you should think about the data from a specific date as data that falls in a range, not at a single point in time. So ideally your query should use a range, such as:
WHERE [Timestamp] >= #Date
AND [Timestamp] < DATEADD(DAY, 1, #Date)
In this case, luckily, the optimizer is smart and will still use an index if you use CONVERT(DATE, [timestamp]) against the column. However in a lot of cases you need to be careful because this will often make your clause non-sargable.
PS Timestamp is a horrible column name. It's a data type in SQL Server which has nothing to do with date or time.
A common technique for truncating the time part off a datetime value is to use the DATEDIFF and DATEADD functions. In your example it would be used like this to truncate the time part of the Timestamp field.
WHERE #DateEntered = DATEADD(DAY,0, DATEDIFF(DAY, 0, Timestamp))
Bascially it's taking the datetime value and finding the name of days since "the date represented by 0" (for lack of a better description) and then adding that number of days back. This effectively truncates time part.
The task:
I need to count every record in a table that was added after 07/01/2011.
Info:
There is a column in the table "Date_added" which is formatted as varchar and contains dates in format mm/dd/yyyy.
What I've tried:
I tried the following query:
SELECT count(date_added) FROM Abatements_Doc WHERE date_added >= '07/01/2011'
Unfortunately it counted any date where the month was greater than 07 regardless of the year or day. I'm at a loss as to how I should format my query to get it to read the dates properly instead of by ascii sort. In my research I discovered the CAST and CONVERT options, but am not sure how to use them, or which one I should use if any. I'm extremely new to SQL, and want to make sure I don't mess up the data in the table. I just need to get the count as specified above without altering the data in the table in any way. Any help in this regard will be very much appreciated. Thanks in advance.
I didn't test. But try convert statement.
SELECT count(date_added)
FROM Abatements_Doc
WHERE convert(datetime,date_added,1) >= convert(datetime,'07/01/2011',1)
(1) don't use mm/dd/yyyy as your date format. Use a safe and unambiguous format; the only one I trust for DATETIME/SMALLDATETIME is YYYYMMDD.
(2) change the data type in your table to DATETIME/SMALLDATETIME/DATE depending on accuracy required. Then `WHERE date_added >= '20110701' will work just fine (and will use an index on that column, if one exists).
(3) if you can't change the data type, then the following will work just fine as well (though no index will be used):
WHERE CONVERT(DATETIME, date_added, 101) >= '20110701'
Varchar can't be compared, try changing your column to date type.
Convert both date_added column values and your target date to DATETIME and compare; as in:
SELECT COUNT(1)
FROM Abatements_Doc
WHERE (CONVERT(datetime, date_added, 101)) >= CONVERT('07/01/2011', date_added, 101))