在 SQLServer 中存储文件

这是我知道的一个老问题，但是对于 SQL Server 2012，最终是否可以在数据库中存储文件，还是应该将它们保存在文件系统中，只在数据库中引用它们？

如果将它们存储在数据库中被认为是可以接受的，那么最有效的方法是什么？

我打算加密，所以我希望处理速度不会太快。

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You might read up on FILESTREAM. Here is some info from the docs that should help you decide:

If the following conditions are true, you should consider using FILESTREAM:

  • Objects that are being stored are, on average, larger than 1 MB.
  • Fast read access is important.
  • You are developing applications that use a middle tier for application logic.

For smaller objects, storing varbinary(max) BLOBs in the database often provides better streaming performance.

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There's still no simple answer. It depends on your scenario. MSDN has documentation to help you decide.

There are other options covered here. Instead of storing in the file system directly or in a BLOB, you can use the FileStream or File Table in SQL Server 2012. The advantages to File Table seem like a no-brainier (but admittedly I have no personal first-hand experience with them.)

The article is definitely worth a read.

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最佳答案

There's a really good paper by Microsoft Research called To Blob or Not To Blob.

Their conclusion after a large number of performance tests and analysis is this:

  • if your pictures or document are typically below 256K in size, storing them in a database VARBINARY column is more efficient

  • if your pictures or document are typically over 1 MB in size, storing them in the filesystem is more efficient (and with SQL Server 2008's FILESTREAM attribute, they're still under transactional control and part of the database)

  • in between those two, it's a bit of a toss-up depending on your use

If you decide to put your pictures into a SQL Server table, I would strongly recommend using a separate table for storing those pictures - do not store the employee photo in the employee table - keep them in a separate table. That way, the Employee table can stay lean and mean and very efficient, assuming you don't always need to select the employee photo, too, as part of your queries.

For filegroups, check out Files and Filegroup Architecture for an intro. Basically, you would either create your database with a separate filegroup for large data structures right from the beginning, or add an additional filegroup later. Let's call it "LARGE_DATA".

Now, whenever you have a new table to create which needs to store VARCHAR(MAX) or VARBINARY(MAX) columns, you can specify this file group for the large data:

 CREATE TABLE dbo.YourTable
(....... define the fields here ......)
ON Data                   -- the basic "Data" filegroup for the regular data
TEXTIMAGE_ON LARGE_DATA   -- the filegroup for large chunks of data

Check out the MSDN intro on filegroups, and play around with it!


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