The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 3: Accessing FILESTREAM Data from Client ApplicationsFROM ItemsFor each row in the result setFor column 1 to 3Open the FILESTREAM data fileRead from FILESTREAM data FileDo something with the dataClose the FILESTREAM data fileNext columnNext rowCommit transactionClose database connection*/Listing 3-25:Pseudocode that shows how to read BLOB data from more than one row and column.Understanding the Logical Path to aFILESTREAM Data FileYou may have noticed by now that FILESTREAM deals with a lot of logical identifiers! Forexample, the FILESTREAM file share, configured while enabling the FILESTREAM feature(see Appendix A) is not mapped to a physical directory on the system; it is simply a logicalidentifier that SQL Server uses internally to point to the FILESTREAM data container. Ifyou try to explore the FILESTREAM share name by double-clicking on it from WindowsExplorer, you will realize that it does not open any folder, as would be expected for a"normal" file share.Just like the FILESTREAM file share, the logical path to a FILESTREAM data file (returnedby the PathName() function) is an internal identifier that SQL Server uses to point tothe disk file associated with a FILESTREAM data value. When a client application wantsto read or write FILESTREAM data through the streaming APIs, it needs to have a wayto exactly pinpoint the FILESTREAM value on a specific table, row, or column. ThePathName() function make this simpler. A client application can run a T-SQL query thatlocates the specific FILESTREAM value and calls the PathName() function to retrieve alogical identifier pointing to it.115