Chris Bell warns against using double dot syntax:
I am finding more and more cases where SQL code is being created using the double dot or period for the 2 part naming convention.
For example, instead of using dbo.table1 I am seeing ..table1.
I don’t know who suggested this in the first place, but it is not a good idea. Sure it works and does what you expect, but there is a HUGE risk with doing this. When you use the .. syntax, you are telling the code to use whatever the default schema is for the user that is running the query. By default that is the dbo schema, but there is no guarantee that all systems are going to be that way.
Read on to understand why this is a big deal.