Riyadh Philanthropic Society For Science Prince Sultan College For Woman Dept. of Computer & Information Sciences CS 340 Introduction to Database Systems (Chapter 5 Tutorial)

Chapter 5 Tutorial1 Exercise Suppose that each of the following update operations is applied directly to the following database state. Discuss all integrity constraints violated by each operation, if any, and the different ways of enforcing these constraints.

Chapter 5 Tutorial2 Exercise - a Insert into EMPLOYEE. No constraint violations.

Chapter 5 Tutorial3 Exercise - b Insert into PROJECT. Violates referential integrity because DNUM=2 and there is no tuple in the DEPARTMENT relation with DNUMBER=2. This constraint can be enforced by: Rejecting the insertion, or Changing the value of DNUM in the new PROJECT tuple to an existing DNUMBER value in the DEPARTMENT relation, or Inserting a new DEPARTMENT tuple with DNUMBER=2.

Chapter 5 Tutorial4 Exercise - c Insert into DEPARTMENT. Violates both the key constraint and referential integrity: Violates the key constraint because there already exists a DEPARTMENT tuple with DNUMBER=4. This constraint can be enforced by: Rejecting the insertion, or Changing the value of DNUMBER in the new DEPARTMENT tuple to a value that does not violate the key constraint. Violates referential integrity because MGRSSN=' ' and there is no tuple in the EMPLOYEE relation with SSN=' '. This constraint can be enforced by: Rejecting the insertion, or Changing the value of MGRSSN to an existing SSN value in EMPLOYEE, or Inserting a new EMPLOYEE tuple with SSN=' '.

Chapter 5 Tutorial5 Exercise - d Insert into WORKS_ON. Violates both the entity integrity and referential integrity: Violates entity integrity because PNO, which is part of the primary key of WORKS_ON, is null. This constraint can be enforced by: Rejecting the insertion, or Changing the value of PNO in the new WORKS_ON tuple to a value of PNUMBER that exists in the PROJECT relation. Violates referential integrity because ESSN=' ' and there is no tuple in the EMPLOYEE relation with SSN=' '. This constraint can be enforced by: Rejecting the insertion, or Changing the value of ESSN to an existing SSN value in EMPLOYEE, or Inserting a new EMPLOYEE tuple with SSN=' '.

Chapter 5 Tutorial6 Exercise - e Insert into DEPENDENT. No constraint violations.

Chapter 5 Tutorial7 Exercise - f Delete the WORKS_ON tuples with ESSN= ' '. No constraint violations.

Chapter 5 Tutorial8 Exercise - g Delete the EMPLOYEE tuple with SSN= ' '. Violates referential integrity because several tuples exist in the EMPLOYEE, DEPARTMENT, WORKS_ON, and DEPENDENT relations that reference the tuple being deleted from EMPLOYEE. This constraint can be enforced by: Rejecting the deletion, or Deleting all tuples in the EMPLOYEE, DEPARTMENT, WORKS_ON, and DEPENDENT relations whose values for SUPERSSN, MGRSSN, ESSN, and ESSN, respectively, is equal to ' '. Modifying the referencing attribute values causing violation by either setting them to null or changing them to reference another valid tuple.

Chapter 5 Tutorial9 Exercise - h Delete the PROJECT tuple with PNAME= 'ProductX'. Violates referential integrity because two tuples exist in the WORKS_ON relation that reference the tuple being deleted from PROJECT. This constraint can be enforced by: Rejecting the deletion, or Deleting the tuples in the WORKS_ON relation whose value for PNO=1. Modifying the referencing attribute values causing violation by either setting it to null or changing it to reference another valid tuple.

Chapter 5 Tutorial Exercise - i Modify the MGRSSN and MGRSTARTDATE of the DEPARTMENT tuple with DNUMBER=5 to ' ' and ’ ', respectively. No constraint violations. 10

Chapter 5 Tutorial Exercise - j Modify the SUPERSSN attribute of the EMPLOYEE tuple with SSN= ' ' to ' '. Violates referential integrity because the new value of SUPERSSN=' ' and there is no tuple in the EMPLOYEE relation with SSN=' '. This constraint can be enforced by: Rejecting the modification, or Inserting a new EMPLOYEE tuple with SSN=' '. 11

Chapter 5 Tutorial Exercise - k Modify the HOURS attribute of the WORKS_ON tuple with ESSN= ' ' and PNO= 10 to '5.0'. No constraint violations. 12