Sql – a ‘multi-part identifier’ and why can’t it be bound


I continually get these errors when I try to update tables based on another table. I end up rewriting the query, change the order of joins, change some groupings and then it eventually works, but I just don't quite get it.

What is a 'multi-part identifier'?
When is a 'multi-part identifier' not able to be bound?
What is it being bound to anyway?
In what cases will this error occur?
What are the best ways to prevent it?

The specific error from SQL Server 2005 is:

The multi-part identifier "…" could not be bound.

Here is an example:

UPDATE  [test].[dbo].[CompanyDetail]

SET Mnemonic = [dbBWKMigration].[dbo].[Company].[MNEMONIC], 
               [Company Code] = [dbBWKMigration].[dbo].[Company].[COMPANYCODE]

WHERE [Company Name] = **[dbBWKMigration].[dbo].[Company].[COMPANYNAME]**

The actual error:

Msg 4104, Level 16, State 1, Line 3 The multi-part identifier
"dbBWKMigration.dbo.Company.COMPANYNAME" could not be bound.

Best Solution

A multipart identifier is any description of a field or table that contains multiple parts - for instance MyTable.SomeRow - if it can't be bound that means there's something wrong with it - either you've got a simple typo, or a confusion between table and column. It can also be caused by using reserved words in your table or field names and not surrounding them with []. It can also be caused by not including all of the required columns in the target table.

Something like redgate sql prompt is brilliant for avoiding having to manually type these (it even auto-completes joins based on foreign keys), but isn't free. SQL server 2008 supports intellisense out of the box, although it isn't quite as complete as the redgate version.