Primary Key:
A Primary Key in a
Example:
Students in Universities are assigned a unique registration number.
Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.
Foreign Key:
Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.
Example:
In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.
Many to One Relationship:
When more than one record in a database table is associated with only one record in another table, the relationship between the two tables is referred as many to one relationship. It is also represented as M: 1 relationship.
One to Many Relationship:
When one record in a database table is associated with more than one record in another table, the relationship between the two tables is referred as one to many relationship. It is also represented as1: M relationship. This is the opposite of many to one relationship.
CROW FOOT ERD:
The Crow Foot ERD is an Entity Relationship Diagram which is used to represent the cardinalities present in the basic ER diagram. It is used to represent the relationships present between two tuples or tables present in the database.

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Chapter 3 Solutions
EPACK DATABASE SYSTEMS WITH LOOSELEAF
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- Process Allocation A Max BCDABC D A Available B C PO 3 0 2 1 4 2 4 2 1 0 0 P1 0 1 0 1 0 2 2 2 P2 1 2 0 0 3 2 1 0 P3 0 1 1 2 1 1 1 2 P4 0 0 1 1 1 - 0 2 1 a) What is the content of the matrix Need? Process PO P1 P2 P3 P4 A Need BC D D ° b) Is the system in a safe state? If yes, give a safe sequence of processes. If not, explain why the system is not in a safe state. c) If a request from process P4 arrives for (1,0,0,0), can the request be granted immediately? Please state the reason.arrow_forwardConsider N processes sharing the CPU in a round-robin fashion (N>=2). Assume that each context switch takes S ms and that each time quantum is Q ms. For simplicity, assume that processes never block on any event and simply switch between the CPU and the ready queue. Also, assume that a process is still in the ready queue while a context switch is happening. a) What happens if Q is much smaller than S? What happens when Q→→ ∞, i.e. is much larger than the maximum turnaround time of all the processes? Be brief (1-2 sentences max) in your answer. b) If you use RR for scheduling, which of the three performance metrics (waiting, response, turnaround time) is more likely to be improved? Why (1-2 sentences max)?arrow_forwardCompute the jackknife estimate of bias and standard error for the correlation statistics from the law82 data using r languagearrow_forward
- Question D.1: Effective Access Time A computer keeps its page tables in memory. Memory access time is 100 nanoseconds (ns). Answer the following questions about the performance of this setup. Show your work. a) What is the effective access time (i.e. reading a word in memory) with no caching and a two-level page table? b) Consider the above scenario but with a TLB having a cache hit rate of 98%. If the TLB takes 20 ns to access, what is the effective access time of this setup when considering this TLB?arrow_forwardThe data law82 in bootstrap library contains LSAT and GPA for 82 law schools. 1. Write you own R code to estimate the correlation between LSAT and GPA scores, and compute the bootstrap estimate of the standard error and bias of the sample correlation. 2. Use the boot function in boot library to compute the bootstrap estimate of the standard error and bias of the sample correlation. Compare your results in 1 with the function output. using r languagearrow_forwardi would like to get help to resolve the following casearrow_forward
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