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Date and Time popular calculations

Antonios Chatzipavlis

Δεν είναι λίγες οι φορές που στα σεμινάρια που κάνω ειδικά στην T-SQL οι μαθητές μου με ρωτάνε για το πως να υπολογίσουν διάφορα πράγματα με τις ημερομηνίες.

Επίσης βλέπω αρκετούς να βασανίζονται στα queries που γράφουν για να κάνουν τους διάφορους υπολογισμούς με τρόπους χαοτικούς και δαπανηρούς στην εκτέλεση.

Για αυτό το λόγο σε αυτό το μικρό άρθρο σας παραθέτω το πως μπορείτε να υπολογίσετε γρήγορα και με σχεδόν μηδενικό κόστος τις δημοφιλέστερες ερωτήσεις με τις ημερομηνίες

declare @givendate datetime = GETDATE();

-- all sql server versions

select    @givendate as CurrentDate
    ,    (YEAR(@givendate) * 100 ) + MONTH(@givendate)    as YYYYMM; -- return type int

-- before sql server 2012

select    @givendate as CurrentDate
    ,    DATEADD(MONTH,DATEDIFF(MONTH,0, @givendate),0) as FirstDayCurrentMonth 
    ,    DATEADD(DAY,-1, DATEADD(MONTH,DATEDIFF(MONTH,0,@givendate)+1,0)) as LastDayCurrentMonth
    ,    DATEADD(MONTH,DATEDIFF(MONTH,0,@givendate)-1,0) as FirstDayPreviousMonth 
    ,    DATEADD(DAY,-(DAY(@givendate)),@givendate) as LastDayPreviousMonth
    ,    DATEADD(MONTH,DATEDIFF(MONTH,0,@givendate)+1,0) as FirstDayNextMonth 
    ,    DATEADD(DAY,-1 , DATEADD(MONTH,DATEDIFF(MONTH,0,@givendate)+2,0)) as LastDayNextMonth;

-- sql server 2012 and above

select    @givendate as CurrentDate
    ,    DATEADD(DAY,1,EOMONTH(@givendate,-1)) as FirstDayCurrentMonth
    ,    EOMONTH(@givendate) as LastDayCurrentMonth
    ,    DATEADD(DAY,1,EOMONTH(@givendate,-2)) as FirstDayPreviousMonth
    ,    EOMONTH(@givendate,-1) as LastDayPreviousMonth
    ,    DATEADD(DAY,1,EOMONTH(@givendate)) as FirstDayNextMonth
    ,    EOMONTH(@givendate,1) as LastDayNextMonth;

-- all sql server versions

select    @givendate as CurrentDate
    ,    DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate),'19000101') as FirstDayCurrentYear
    ,    DATEADD(DAY,-1, DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate)+1,'19000101')) as LastDayCurrentYear
    ,    DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate)-1,'19000101') as FirstDayPreviousYear
    ,    DATEADD(DAY,-1, DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate),'19000101')) as LastDayPreviousYear
    ,    DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate)+1,'19000101') as FirstDayNextYear
    ,    DATEADD(DAY,-1, DATEADD(YEAR,DATEDIFF(YEAR,'19000101',@givendate)+2,'19000101')) as LastDayNextYear;

-- all sql server versions

select    @givendate as CurrentDate
    ,    DATEADD(SECOND,(60*60*24)-1,DATEADD(DAY,0,DATEDIFF(DAY,0,@givendate))) as MidnightToday
    ,    DATEADD(SECOND,(60*60*24)-1,DATEADD(DAY,-1,DATEDIFF(DAY,0,@givendate))) as MidnightYesterday
    ,    DATEADD(SECOND,(60*60*24)-1,DATEADD(DAY,1,DATEDIFF(DAY,0,@givendate))) as MidnightTommorow
    ,    DATEADD(HOUR,12,DATEADD(DAY,0,DATEDIFF(DAY,0,@givendate))) as NoonToday
    ,    DATEADD(HOUR,12,DATEADD(DAY,-1,DATEDIFF(DAY,0,@givendate))) as NoonYesterday
    ,    DATEADD(HOUR,12,DATEADD(DAY,1,DATEDIFF(DAY,0,@givendate))) as NoonTommorow


Antonios Chatzipavlis

Antonios Chatzipavlis

Antonios is a Data Solutions Consultant and Trainer. He has been working in IT since 1988. In his career, he has worked as senior developer, IT Manager, Solutions Architect and IT Consultant. Since 1995 he has been devoted on new technologies and software development tools, mainly by Microsoft, either by training company staff and colleagues or assisting them in design, development and implementation as a consultant or chief developer. He has focused in Databases and Data Science since 1995. He specialized in Microsoft SQL Server since version 6.0 in areas like SQL Server Internals, Database Design and Development, Business Intelligence and in 2010 he has started working with Azure Data Platform, NoSQL databases, Big Data Technologies and Machine Learning. He is an active member of many IT communities in Greece, answering colleagues' questions and writing articles in his web site. He is the owner of SQLschool.gr which is a community portal with a lot of information about Microsoft SQL Server. He has been a Microsoft Certified Trainer (MCT) since 2000. Microsoft honored him as MVP on Data Platform due to his activities in SQL Server since 2010. He holds a large number of Microsoft Certifications and Microsoft SQL Server Certifications since version 6.5.

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