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Consider the relations described below: PHYSICIAN (regno, name, telno, city)PATIENT (pname, street, city) VISIT (pname, regno, date_of_visit, fee) Where the regno and pname identify the physician and the patient uniquely corresponding. Express queries (i) to (iii) in SQL.(i) Get the name and regno of physicians who are in Delhi.(ii) Find out the name and city of patient(s) who visited a physician on 31 August 2004.(iii) Get the name of the physician and the total number of patients who have visited her.(iv) What does the subsequent SQL query answer SELECT DISTINCT nameFROM PHYSICIAN PWHERE NOT EXISTS( SELECT *FROM VISITWHERE regno = p.regno )
(i) Select name, regno from PHYSICIAN where city = ‘Delhi'; (ii) Select pname, city from PATIENT,VISIT where PATIENT.pname=VISIT.pname and date_of_visit = '31-Aug-04'; (iii) select name, count(*) from PHYSICIAN, VISIT where PHYSICIAN.regno = VISIT.regno group by Physician . regno; (iv) This will provide the name of physicians who have not visited any patient.
What is the used of specifying alias? Specifying alias: is used to rename column or attribute in a table.
A constraint named less_than_20 was defined on the field date_of_birth of table student. Delete this constraint. ALTER TABLE student DROP CONSTRAINT less_than_20;
What are the two integrity rules? Ans: The two integrity rules are: Entity Integrity Rule & Referential Integrity Rule. Entity Integrity Rule - If the attribute A of rel
Increased overheads on update : On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the rel
Define outer union operation of the relational algebra. Compute the outer union for the relations R and S given below. Outer Join - If there are any values in one tabl
non numeric literals
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Explain the systems development life cycle. This is the traditional method to develop, maintain, and replace information systems that contains the project identification and se
Define the concept of aggregation. Give two examples where this concept is useful. Ans: Aggregation transforms a relationship among the objects into a higher-level object. A
For Colorado customers calculate the number of single products ordered. If a product is purchased on multiple orders, it should be counted only single time. The result should conta
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