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Πως μπορώ να μετρήσω το μέγεθος των δεδομένων που έχω μέσα σε ένα blob field?

Antonios Chatzipavlis

Σημέρα ένας αγαπητός συνάδελφος έρχεται στο γραφείο μου και μου κάνει την εξής ερώτηση:

«Υπάρχει κανένας τρόπος με τον οποίο μπορώ να δω το μέγεθος των πραγματικών δεδομένων που έχουν αποθηκευτεί στην βάση μου σε ένα πεδίο τύπου image;»

Σίγουρα η πρώτη σκέψη όλων μας θα πάει στην LEN(), αλλά αυτή όμως δεν παίζει με πεδία τύπου image, text, ntext.

Αντί για αυτή μπορούμε να χρησιμοποιήσουμε την DATALENGTH() η οποία επιστρέφει το μέγεθος σε bytes και η οποία φυσικά μπορεί να χρησιμοποιηθεί και για όλα τα άλλα data types του SQL Server.

Ένα παράδειγμα

Έστω ότι έχω τον πίνακα Α

CREATE TABLE A ( ID INT PRIMARY KEY NOT NULL, PHOTO IMAGE )

Μπορώ να διαβάζω το πραγματικό αποθηκευμένο μέγεθος στο πεδίο PHOTO με ένα απλό query

SELECT  ID, DATALENGTH(PHOTO) SizeInBytes, DATALENGTH(PHOTO)/1024 SizeInKB FROM A

Αυτά για την ώρα, καλή σας ημέρα και καλό SQL Server programming ;)

 


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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