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John Huang’s Blog

John Huang, Microsoft Certified Master in SQL Server, SQL Server MVP, is an independent SQL Server consultant in Vancouver BC, Canada. He started using SQL Server for his projects in year 1994. He has architected and implemented many SQL and BI applications serving different industrial areas. He loves talking about SQL Server and discussing SQL Server technologies with others. He blogs at http://www.sqlnotes.info.

Archives: May 2013

Len() and DataLength()

Both system functions, Len() and DataLength(), in SQL Server are used to measure the length of the data. The main difference of those 2 is that Len() gets the string length of the data in which DataLength measures the storage length of the data.

Len always converts the input to… Read more

1 comments, 377 reads

Posted in John Huang’s Blog on 16 May 2013

Protect Yourself from Using DBCC WritePage

I blogged DBCC WritePage a year ago here http://www.sqlnotes.info/2011/11/23/dbcc-writepage/. It’s an extremely dangerous command especially with the last parameter “directORbufferpool” of this command turned on. I also showed you how to fix the page checksum here http://www.sqlnotes.info/2013/05/02/fix-page-checksum/. To protect yourself, please ensure you are operating on the database… Read more

0 comments, 269 reads

Posted in John Huang’s Blog on 14 May 2013

Bring Offline File Online — Modify SQL Server Metadata

In my last post, I demonstrated how to mount a database with missing NDF files. In the end, we still have issues removing tables created over missing files, the files are taken offline. Be cautious of taking files offline since there is no (official) way to bring it back… Read more

2 comments, 330 reads

Posted in John Huang’s Blog on 9 May 2013

Attach Database with Missing NDF File

I wonder if you’ve had the situation that I had before where you have to attach a database with one or few missing .ndf files. It seems pretty common since I’ve just seen the same scenario at one of my clients. The reasons behind it are quite similar – They… Read more

12 comments, 1,233 reads

Posted in John Huang’s Blog on 7 May 2013

Fix Page Checksum

A checksum value is tagged with every data page in SQL Server. This is used to detect issues on the storage system to ensure what has been read from the disk is what has been written to the disk. When the checksum is detected which is not the one it’s… Read more

4 comments, 398 reads

Posted in John Huang’s Blog on 2 May 2013