Can we create index on primary key column?
When you create a PRIMARY KEY constraint, a unique clustered index on the column or columns is automatically created if a clustered index on the table does not already exist and you do not specify a unique nonclustered index. The primary key column cannot allow NULL values.
Can we create index on identity column?
As a general practice you would create a unique index on your identity column, this speeds up lookups. Usually you would like your identity columns to be ‘clustered indexes’ as well ( Id int identity primary key is the shortcut notation), meaning table is layed out on disk in the same order your identity column is.
How big is an index on A varchar column?
As you might know, the key columns of an index in SQL Server (Clustered Index, Non-Clustered Index) have a size limitation of a maximum of 900 bytes. Imagine now that you want to fool SQL Server, and create an index on a VARCHAR(8000) column and insert more than 900 bytes in the index key column.
When to create a non clustered index on A varchar?
If you create a non-clustered index on a varchar (>900) column you will receive a warning message when creating the index. If you create a clustered index on a varchar (>900) column you will receive a warning message when creating the index.
What is VARCHAR ( MAX ) column in SQL Server?
My situation is that I have an SQL Server 2008 database table that has a varchar (max) column usually filled with a lot of text.
What happens when you create an index on a column?
If you create an index on a column that its definition is longer than 900 or 1700 (depending on version and type of index), you’ll either get a warning and the index creation will succeed (if the table is empty or the existing data are not that long) or an error and the index creation will fail (if a row or more exceed the limit).