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DBCC CHECKIDENT - Manually set a new current identity value for the identity column

Antonios Chatzipavlis

Δεν είναι σπάνιο το να έχεις ένα identity field μέσα σε ένα πίνακα. Κάποια στιγμή πιθανότατα θέλεις να σβήσεις όλα τα δεδομένα του πίνακα και όταν αρχίσεις να γεμίζεις ξανά τον πίνακα θέλεις το identity field να ξεκινάει από την αρχή.

Πιθανότατα να γνωρίζεις ότι αντί να κάνεις DELETE FROM table το οποίο δεν αρχικοποιεί ξανά το identity field μπορείς να κάνεις TRUNCATE TABLE το οποίο αρχικοποιεί ξανά το identity field.

Όμως δεν μπορείς να κάνεις TRUNCATE TABLE καθώς αυτός ο πίνακας έχει referential integrity με άλλους πίνακες και για να κάνεις truncate θα πρέπει να ξηλώσεις όλα τα referential integrity constraints.

Επειδή αυτό είναι κάτι το οποίο ρωτάνε αρκετοί η απάντηση είναι απλή και ακούει σε ένα dbcc statement που δεν είναι άλλο από το DBCC CHECKIDENT το οποίο υπάρχει από τον SQL Server 2005 και μετά και το documentation του στα BOL είναι το παρακάτω (κάνω copy ένα μέρος του για την ευκολία στην ανάγνωση σας, το original υπάρχει εδώ)

Προσέξτε την δυνατότητα του RESEED!


DBCC CHECKIDENT  (from BOL)

Checks the current identity value for the specified table in SQL Server 2014 and, if it is needed, changes the identity value. You can also use DBCC CHECKIDENT to manually set a new current identity value for the identity column.

Syntax
 
DBCC CHECKIDENT
 (
    table_name
        [, { NORESEED | { RESEED [, new_reseed_value ] } } ]
)
[ WITH NO_INFOMSGS ]
 
[ WITH NO_INFOMSGS ]

Arguments

 
table_name
Is the name of the table for which to check the current identity value. The table specified must contain an identity column. Table names must comply with the rules for identifiers.

NORESEED
Specifies that the current identity value should not be changed.

RESEED
Specifies that the current identity value should be changed.

new_reseed_value
Is the new value to use as the current value of the identity column.

WITH NO_INFOMSGS
Suppresses all informational messages.

Ελπίζω να μην ξεχάσετε όταν θα αντιμετωπίσετε το ίδιο θέμα ξανά


/*antonch*/
 


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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