I have creating TestDE Data extension using these attributes like SubscriberKey, AccountID, EventDate, Date, Month, Year attributes. And Created with same attributes using Target Data extension. Now my requirement is how to write a SQL query on '_Open' for Split date, Month and Year. Can anybody help on this.
You can use Datepart() function. In your case it would be
select Datepart(year, EventDate) as Year, Datepart(month, EventDate) as Month ... from _Open