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Nested CTE – A Simple Sample

Antonios Chatzipavlis
Friday 01 March 2013

Σε αυτό το σύντομο post θα σας δείξω κάτι για το οποίο έχω ερωτηθεί αρκετές φορές και δεν είναι άλλο από το πώς μπορώ να έχω nested CTE statements.

Αρκετοί πιστεύουν ότι αυτό μπορεί να γίνει βάζοντας το ένα μέσα στο άλλο, όμως κάτι τέτοιο συντακτικά δεν είναι επιτρεπτό.

Γι’ αυτό το λόγο σας παραθέτω ένα απλό παράδειγμα το οποίο είναι εύκολα κατανοητό

      SELECT * FROM (VALUES (1),(2),(3),(4),(5)) AS T(A)
) ,
      SELECT *, 'T2' AS B FROM T1
) ,
      SELECT *,'T3' AS C FROM T2

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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