Is there a way to create a table with the following?
Label
“week #1: 1/1/18 - 1/7/18”
“week #2: 1/8/18 - 1/15/18”
And so forth?
Basically, I’m looking for the week number and the date range that week includes.
I think what you want as a starting point, is a "date dimension" or "calendar table". Here's one of many examples for creating them (creating them is not really the issue though, it's how you use them that's more important).
In your example, it looks like you want to pivot the data (create a crosstab). As a rule of thumb, you're generally better off pivoting on the client application, than you are persisting that denormalised anti-pattern in a relational database.
Here's a fictitious example:
DECLARE #start_date as datetime = '20180301';
DECLARE #end_date as datetime = dateadd(dd,datediff(dd,0,GETDATE()),0);--midnight last night
SELECT cal.week_starting --The date of the start of the week eg 15 April 2018.
,dateadd(d,6,cal.week_starting) as week_ending -- The date of the last day of the week eg 21 April 2018. You can cast as varchar, format and concatenate to the previous field to suit yourself.
,my_events.my_category
,count(*) as recs
FROM my.CALENDAR cal
JOIN dbo.big_list_of_events my_events ON cal.census_dttm = my_events.event_date
WHERE my_events.event_date >= #start_date
and my_events.event_date < #end_date
GROUP BY cal.week_starting
,my_events.my_category
ORDER BY cal.week_starting
,my_events.my_category
;
Once you get to this point you're ready to query it with your client application (eg Pivot Tables in Excel) and slice and dice to your heart's content. Again, you probably don't want data stored in your db as a crosstab.
Related
I am using the latest SQL Server. I have a table with a CreatedDate column. I need to write a Query that uses dates that are plus or minus 7 from the Date in CreatedDate. I have no clue how to go about this. My thought was this:
DECLARE #Date datetime
DECLARE #SevenBefore datetime
DECLARE #SevenAfter datetime
SET #Date = CreatedDate
SET #SevenBefore = DATEADD(day,-7,#Date)
SET #SevenAfter = DATEADD(day,7,#Date)
SELECT *
FROM <table>
WHERE <table> BETWEEN #SevenBefore AND #SevenAfter
The issue with this is that I cannot use "CreatedDate" as a SET #DATE because SQL gives an error "Invalid column name 'CreatedDate'"
Any help would be appreciated. I cannot list a date because every date in that column could be different.
Thanks
In this case, you need to stop thinking as a programmer would, and start thinking as a Database programmer would.
Lets work only with this central part of your query:
SELECT *
FROM <table>
WHERE <table> BETWEEN #SevenBefore AND #SevenAfter
Now, you say that the CreatedDate is a column in a table. For this example, I will assume that the CreatedDate is in a table other than the one in your example above. For this purpose, I will give two fake names to the tables. The table with the CreatedDate, I will call tblCreated, and the one from the query above I will call tblData.
Looking above, it's pretty obvious that you can't compare an entire table row to a date. There must be a field in that table that contains a date/time value. I will call this column TargetDate.
Given these assumptions, your query would look something like:
SELECT *
FROM tblCreated tc
INNER JOIN tblData td
ON td.TargetDate BETWEEN DATEADD(day, -7, tc.CreatedDate) and DATEADD(day, 7, tc.CreatedDate)
Looking at this, it is clear that you still need some other associations between the tables. Do you only want all data rows per customer based on the Created date, or perhaps only want Creations where some work was done on them as shown in the Data records, or ??. Without a fuller specification, we can't help with that, though.
I have a table of database size information. The data is collected daily. However, some days are missed due to various reasons. Additionally we have databases which come and go over or the size does not get recorded for several databases for a day or two. This all leads to very inconsistent data collection regarding dates. I want to construct a SQL procedure which will generate a percentage of change between any two dates (1 week, monthly, quarterly, etc.) for ALL databases The problem is what to do if a chosen date is missing (no rows for that date or no row for one or more databases for that date). What I want to be able to do is get the nearest available date for each database for the two dates (begin and end).
For instance, if database Mydb has these recording dates:
2015-05-03
2015-05-04
2015-05-05
2015-05-08
2015-05-09
2015-05-10
2015-05-11
2015-05-12
2015-05-14
and I want to compare 2015-05-06 with 2015-05-14
The 2015-05-07 date is missing so I would want to use the next available date which is 2015-05-08. Keep in mind, MyOtherDB may only be missing the 2015-05-06 date but have available the 2015-05-07 date. So, for MyOtherDb I would be using 2015-05-07 for my comparison.
Is there a way to proceduralize this with SQL WITHOUT using a CURSOR?
You're thinking too much into this, simple do a "BETWEEN" function in your where clause that takes the two parameters.
In your example, if you perform the query:
SELECT * FROM DATABASE_AUDIT WHERE DATE BETWEEN param1 /*2015-05-06*/ and param2 /*2015-05-14*/
It will give you the desired results.
select (b.dbsize - a.dbsize ) / a.dbsize *100 dbSizecChangePercent from
( select top 1 * from dbAudit where auditDate = (select min(auditDate) from dbAudit where auditDate between '01/01/2015' and '01/07/2015')) a
cross join
(select top 1 * from dbAudit where auditDate = (select max(auditDate) from dbAudit where auditDate between '01/01/2015' and '01/07/2015')) b
The top 1 can be replaced by a group by. This was assuming only 1 db aduit per day
I have a table with the following structure:
CREATE TABLE MyTable (
ID int identity,
Whatever varchar(100),
MyTime time(2) NOT NULL,
MyDate date NOT NULL,
MyDateTime AS (DATEADD(DAY, DATEDIFF(DAY, '19000101', [MyDate]),
CAST([MyDate] AS DATETIME2(2))))
)
The computed column adds date and time into a single datetime2 field.
Most queries against the table have one or more of the following clauses:
... WHERE MyDate < #filter1 and MyDate > #filter2
... ORDER BY MyDate, MyTime
... ORDER BY MyDateTime
In a nutshell, date is usually used for filtering, and full datetime is used for sorting.
Now for questions:
What is the best way to set indices on those 3 date-time columns? 2 separate on date and time or maybe 1 on date and 1 on composite datetime, or something else? Quite a lot of inserts and updates occur on this table, and I'd like to avoid over-indexing.
As I wrote this question, I noticed the long and kind of ugly computed column definition. I picked it up from somewhere a while ago and forgot to investigate if there's a simpler way of doing it. Is there any easier way of combining a date and time2 into a datetime2? Simple addition does not work, and I'm not sure if I should avoid casting to varchar, combining and casting back.
Unfortunately, you didn't mention what version of SQL Server you're using ....
But if you're on SQL Server 2008 or newer, you should turn this around:
your table should have
MyDateTime DATETIME
and then define the "only date" column as
MyDate AS CAST(MyDateTime AS DATE) PERSISTED
Since you make it persisted, it's stored along side the table data (and now calculated every time you query it), and you can easily index it now.
Same applies to the MyTime column.
Having date and time in two separate columns may seem peculiar but if you have queries that use only the date (and/or especially only the time part), I think it's a valid decision. You can create an index on date only or on time or on (date, whatever), etc.
What I don't understand is why you also have the computed datetime column as well. There s no reason to store this value, too. It can easily be calculated when needed.
And if you need to order by datetime, you can use ORDER BY MyDate, MyTime. With an index on (MyDate, MyTime) this should be ok. Range datetime queries would also be using that index.
The answer isn't in your indexing, it's in your querying.
A single DateTime field should be used, or even SmallDateTime if that provides the range of dates and time resolution required by your application.
Index that column, then use queries like this:
SELECT * FROM MyTable WHERE
MyDate >= #startfilterdate
AND MyDate < DATEADD(d, 1, #endfilterdate);
By using < on the end filter, it only includes results from sometime before midnight of that date, which is the day after the user-selected "end date". This is simpler and more accurate than adding 23:59:59, especially since stored times can include microseconds between 23:59:59 and 00:00:00.
Using persisted columns and indexes on them is a waste of server resources.
How I can calculate the working time in SQL Server between two datetime variables, excluding the holidays?
Any ideas?
Holidays aren't universal - they depends very much on your location. Not even the fact which days of the week are "working" days is the same - it depends on your location.
Because of that, a general, universal answer will not be possible, and for that reason, there's also no system-provided function in T-SQL for doing this. How would SQL Server know what holidays you have in your corner of the world??.
You need to have a table of your holidays somewhere in your system and handle it yourself.
Some posts that might be of some help to you:
Calculate Number of Working Days in SQL Server: this just basically removes any Saturdays and Sundays - but doesn't include other holidays
How do I count the number of business days between two dates? : shows the same main approach, with the addition of a table that contains other holidays like Easter, 4th of July (US National Holiday) and so on
Like marc_s says, you currently need a custom solution. I really hope Microsoft adds some standard functionality: it's tough to get right, and holidays are pretty much standardized by location.
Here's an example:
declare #start_date datetime
declare #end_date datetime
set #start_date = '2010-12-20'
set #end_date = '2010-12-26'
-- A table with all non-working days. This just adds Christmass, but you
-- probably should add weekends as well.
declare #non_working_days table (dt datetime)
insert #non_working_days values ('2010-12-25'), ('2010-12-26')
-- Remove the time part
set #start_date = DATEADD(D, 0, DATEDIFF(D, 0, #start_date))
set #end_date = DATEADD(D, 0, DATEDIFF(D, 0, #end_date))
-- Find the number of non-working-days
declare #nwd_count int
select #nwd_count = count(*)
from #non_working_days
where dt >= #start_date and dt < #end_date
-- Print result
select datediff(DAY, #start_date, #end_date) - #nwd_count
This prints 5, because the 25th is not a working day.
Have a table which has a row for every date you're interested in, and, say, a "working hours" column, or just a "working day" indicator if you want to do it at day granularity. (I find this approach makes the final SQL simpler, plus enables all sorts of other useful queries, but then I'm into data warehousing, rather than operational databases, so you may find the "just list the holidays" approach better, depending...)
You will, of course, have to create that table yourself, working from some feed of holiday dates for the region you're interested in.
Typically you can project these forward at least a year, as most public holidays are agreed a long way in advance (though there are some that pop up at the "last minute" -- in the UK, for example, 29 April will be an extra public holiday in 2010, as there's a royal wedding taking place, and we got less than a year's notice of that.
Then you just
SELECT
SUM(working_hours)
FROM
all_dates
WHERE
the_date BETWEEN #start_date AND #end_date
If you want to do this internationally, it gets incredibly difficult to get your data; there's no sensible source that I know of for international holiday dates, and different regions in a "country" might have different dates -- e.g. you may know that someone's in the United Kingdom, but unless you know if they're in Scotland or not, you won't know if the first two days of the year are a public holiday, or just the first...
I have an appointments table with appointments for a number of 'resources'
what i need to do is query that and return (for a particular resource) all free appointment slots across a date range.
i had thought the best way to approach this would be to generate a temp table of possible appointment times (as the length of appointment may be 30/60/90 minutes - the appointment length would be specified for the query.) and then select the intersect of those two recordsets. i.e. all of those - across the date range - where there are NOT appointments in the appointments table. thus returning all possible appointments for that resource.
or maybe just - again - generate the records of possible appointment datetimes, and then except the actual appointments already booked..?
unless of course someone can suggest an easier option.?
also not entirely sure how to generate the table of possibles ie a table with records for 2010-12-08 09:00, 2010-12-08 10:00, and so on (for 1 hr appointments)...
any ideas?
edit: have a vague idea on the possibles...
DECLARE #startDate DateTime
DECLARE #EndDate DateTime
set #startDate = '2010-12-08 09:00'
set #endDate = '2010-12-11 09:00';
with mycte as
(
select cast(#startDate as datetime) DateValue
union all
select dateadd(mi,30,DateValue)
from mycte
where DateValue <= #endDate
and datepart(hh, dateadd(mi,30,DateValue)) Between 9 AND 16
)
select DateValue
from mycte
This is a classic gaps and islands problem. It essentially a common problem where you need to identify missing values (gaps) in a sequence. Fortunately there is a free sample chapter on this very topic from the Manning book, SQL Server MVP Deep Dives. Hopefully it will provide inspiration as it gives guidance on a number of possible approaches.
http://www.manning.com/nielsen/SampleChapter5.pdf
Here is Itzik Ben-Gan's description of the problem, quoted from the above chapter.
Gaps and islands problems involve
missing values in a sequence
... The sequences involved can also
be temporal, such as order dates, some
of which are missing due to inactive
periods (weekends, holidays). Finding
periods of inactivity is an example of
the gaps problem, and finding periods
of activity is an example of the
islands problem.