Sql-server – Selecting with varbinary(max) criteria (in the where clause)

arrayblobsql-server-2008-r2

Basic info

Database: SQL Server Express 2008 R2
Client: SQL Server Management Studio

Backround (skip if not interested):

A project I'm maintaining uses an ORM, which apparently stored my enum values (which inherit from Byte) into binary serialized .Net objects stored in a varbinary(max) field.
I only found out this was happening after a new requirement emerged dictating my code to run under medium trust. Since the .Net binary formatter needs full trust to be called, it started crashing on the enums.

To clean the mess up I need to create migration scripts that will convert these (varbinary(max)) values back to integer values. There are only a handful of different values so it shouldn't be a big problem (I thought).

The problem:

I am able to get string representations of the blobs when selecting:

SELECT BinValue FROM MyTable where Type = 'Object';

It returns a string '0x…(an array of hexadecimal values)'.

But when I try to select on the column using copy-and-paste making sure I have the exact binary equivalent:

SELECT ItemId FROM MyTable WHERE Value=convert(varbinary(max), '0x...')

it does not return any records.

So is it possible to solve this using a client (such as Management Studio)?

If so, what would be the correct syntax?

Best Answer

Just do

SELECT ItemId
FROM   MyTable
WHERE  Value = 0xAAFF

You are converting the varchar representation to varbinary(max) which is not correct.

SELECT CONVERT(VARBINARY(MAX), '0xAAFF') returns 0x307841414646 for me for example. It will give you a result based on the character codes in that string representation in your default collation's code page.

Related Solutions

Sql-server – Would I lose data if I change a column from varbinary(8000) to varbinary(max)

No, you won't lose data.

SQL Server will do an in place conversion, as a transaction. This means if anything fails, it will rollback.

Note, this is more than a simple metadata change so it may take some time because data has to be moved around

Sql-server – Migrating from text and image to varchar(max) and varbinary(max)

Just a note: these new data types support the same sizes as the deprecated types they replace, e.g. 2GB of data (which means a different number of characters depending on Unicode and other factors).

One thing for sure is you should parse all of your existing application code, stored procedures, functions etc. for instances of built-ins like UPDATETEXT, READTEXT, TEXTPTR, WRITETEXT, TEXTSIZE and @@TEXTSIZE - all of which will likely have to be changed. You can identify those stored in SQL Server this way:

SELECT s.name, o.name
  FROM sys.sql_modules AS m
  INNER JOIN sys.objects AS o
  ON m.[object_id] = o.[object_id]
  INNER JOIN sys.schemas AS s
  ON o.[schema_id] = s.[schema_id]
  WHERE UPPER(m.definition) LIKE N'%UPDATETEXT%'
     OR UPPER(m.definition) LIKE N'%WRITETEXT%'
     OR UPPER(m.definition) LIKE N'%READTEXT%'
     OR UPPER(m.definition) LIKE N'%TEXTPTR%'
     OR UPPER(m.definition) LIKE N'%TEXTSIZE%';

Note that this could yield false positives (e.g. those terms may be in a comment or naturally occur in an entity name) and it could miss some (e.g. the commands could be constructed using parameters / dynamic SQL). You're on your own for searching your application codebase and/or source control for instances of the same.

Also make sure you find all modules that accept or output parameters of these types:

SELECT DISTINCT s.name, o.name
  FROM sys.parameters AS p
  INNER JOIN sys.objects AS o
  ON p.[object_id] = o.[object_id]
  INNER JOIN sys.schemas AS s
  ON o.[schema_id] = s.[schema_id]
  WHERE system_type_id IN (34,35,99);

You might also want to consider that you may have logic in jobs and other maintenance routines that currently avoid these tables or treat them differently because of the limitations inherent in these data types. When you move to the newer types (and especially on the most modern versions of SQL Server), a lot of these limitations go away.

Finally, other than the syntax above, I can't think of a single feature the old types support that the new types don't.

Best Answer

Related Solutions

Sql-server – Would I lose data if I change a column from varbinary(8000) to varbinary(max)

Sql-server – Migrating from text and image to varchar(max) and varbinary(max)

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