A very misleading line in the SQL server 70-431 book states “…keep in mind that indexes are limited to a maximum of 900 bytes.” Was not sure what this meant, but became much clearer after referring to MSDN
Just to clarify it is the sum of the lengths of the fixed-size columns that make up the index that cannot exceed 900 bytes. Below is a way of determining the size of a potential index: |  |
| SELECT SUM(max_length)AS TotalIndexKeySize FROM sys.columns WHERE name IN (N'AddressLine1', N'AddressLine2', N'City', N'StateProvinceID', N'PostalCode') AND object_id = OBJECT_ID(N'Person.Address'); |
SQL Server
sql server, 70-431