Relational algebra.pptx
- 2. Relational algebra is a procedural query language. It uses operations to perform queries. It gives a step by step process to obtain the result of the query.
- 3. Types of Relational operation
- 4. Select operator selects tuples(rohs) that satisfy a given predicate. It‘s an denoted by sigma (σ). Notatin in σ p(r) Where., σ is used for selection prediction. r is ised to relation. p is used as a propositional logic formula which may be use connection like:AND OR and NOT. These relational can use as relational operators like=, ≠, ≥,<,>, ≤
- 5. NAME AGE WEIGHT Harry 34 80 Saily 26 64 George 29 70 Helena 54 54 Peter 34 80 NAME AGE WEIGHTH Harry 34 80 Helena 54 54 Peter 34 80 σ age≥34(PERSON) Name Age Weighth Helena 54 54 Σ age=weight(PERSON)
- 6. This operation shows the list of those attributes that we wish to appear in the result. Rest of the attributes are eliminated from the table. It’s denoted by (π). Where.., A1,A2,A3 is used as an attribute of relation r.
- 7. NAME STREET CITY jones Main Harrison Smith North Rye Hays Main Harrison Curry North Rye Brooks Senator Brooklyn Johnson Aima Brooklyn Input: πNAME, CITY(CUSTOMER) Output: NAME CITY Johns Harrizon Smith Rye Hays Harrison Curry Rye Brooke Brooklyn Johnson Brooklyn
- 8. Union operation combines values in R,Sby removing duplicate ones. This operation does not need the two tables being operated on to be union compatible. It elimimates the duplicate tuples. It’ denoted by U. Notation: R U S a union operation must hold the following condition. 1. R.and S must have the attribute of the. Same number. 2. Dupicte tuples are eliminted automatically.
- 9. Customer_Na me Account_no Johnson A-101 Smith A-121 Mayes A-321 Turner A-176 Johnson A-273 Johns A-472 Lindsay A-284 BORROW RELATION:- Customer_na me Loan_no Jones L -17 Smith L -23 Hayes L -15 Jackson L -14 Curry L -93 Smith L -11 Williams L -17
- 10. INPUT: π CUSTOMER_NAME(BORROW)u π customer_name(DEPOSITER CUSTOMER_NAME johnson Smith Hayes Jones Turner Lindsay Jackson Curry Williams Mayes OUTPUT:-
- 11. Suppose there are two TUPLES R and S. The set intersection operation contains all TUPLES that are in both R & S. It is denoted by intersection ∩. Notation: R ∩ S EXAMPLE: Using the above DEPOSITOR table and BORROW table INPUT: ∏ CUSTOMER_NAME (BORROW) ∩ ∏ CUSTOMER_NAME (DEPOSITOR) OUTPUT:
- 12. Suppose there are two tuples R and S. The set intersection operation contains all tuples that are in R but not in S. It is denoted by intersection minus (-). Notation: R - S EXAMPLE: Using the above DEPOSITOR table and BORROW table INPUT: ∏ CUSTOMER_NAME (BORROW)-∏ CUSTOMER_NAME (DEPOSITOR) OUTPUT:
- 13. The Cartesian product is used to combine each row in one table with each row in the other table. It is also known as a cross product. It is denoted by X. Notation: E X D EXAMPLE:
- 16. The rename operation is used to rename the output relation. It is denoted by rho (ρ). EXAMPLE: We can use the rename operator to rename STUDENT relation to STUDENT1. ρ(STUDENT1, STUDENT)