Select operators or set operators

Also called a set operators

Union:
This is combines the results of two queries and returns the set of distinct rows returned by either query.
Union All:
This is combines the results of two queries and returns all rows returned by either query,including  duplicates.
Intersect:

This combines the results of two queries and returns the set of distinct rows returned by both queries

Minus:

This combines the results of two queries and returns the distinct rows that were in the first query, but not in the second

 
Other select operators

(+)Denotes that the preceding column is an outer join

* wildcard operator.Equals all columns in a select statement 

Prior Denotes a parent-child relation ship operator in prior