The two types of relational calculus are Tuple Relational Calculus (TRC) and Domain Relational Calculus (DRC). The main differences between the two are as follows:
Scope: TRC is concerned with selecting tuples from relations based on a set of conditions, while DRC is concerned with selecting domains, or sets of values, that satisfy a given condition.
Expressive Power: DRC is more expressive than TRC, as it allows for a wider range of logical formulas and expressions to be used in queries. DRC can also handle queries that are difficult or impossible to express in TRC.
Notation: TRC uses an existential quantifier (∃) to specify conditions on tuples, while DRC uses a universal quantifier (∀) to specify conditions on domains. TRC also uses a tuple variable to represent a row in a relation, while DRC uses a range variable to represent a domain of values.
Readability: TRC is generally more readable and intuitive than DRC, as it closely resembles the SQL query language used in many relational databases. DRC can be more difficult to read and understand, especially for users who are not familiar with mathematical notation and logic.
In summary, TRC and DRC are two types of relational calculus that are used to specify queries in a relational database. TRC is focused on selecting tuples from relations based on a set of conditions, while DRC is focused on selecting domains, or sets of values, that satisfy a given condition. While TRC is more intuitive and closely resembles SQL, DRC is more expressive and can handle more complex queries.
