How to tell if a key in the sql server is identity

SELECT is_identity 
FROM sys.columns 
WHERE object_id = object_id('Nome_da_sua_tabela') 
AND name = 'Nome_da_sua_coluna'

It will return 1 if the column is identity

Complementing the response of @Artur, if you want a relation (table / column) of all the identity keys of a given database:

select o.name, c.name
from sys.objects o inner join sys.columns c on o.object_id = c.object_id
where c.is_identity = 1

You can use COLUMNPROPERTY for this.

select columnproperty(object_id('NomeTabela'),'NomeColuna','IsIdentity')

This will return one of the options:

• 1 = TRUE

• 0 = FALSE

• NULL = The entry is not valid.