relational calcululus

• RC operates on basis of {tuple in set where t is a member of table(with given condition for [attribute])}

  
• RC is like predicates, defines data not steps, unlike R algebra
• To get projection in RC, need to use filtering with additional variables and There Exists where condition = t(condition)

  
• to get union (soft ^) in RC, use ^ to link the chosen (projection) statements

  
• to find data across tables (usually done by natural join), just create different variables with a selection-like match criteria and a value condition to one of them

  
• can also use not exists to act like a - (subtract) operator