CoolInterview.com - World's Largest Collection of Interview Questions & Answers, FAQs, queries, sample papers, exam papers, dumps, what, why, how, where, when questions
Our Services
Get 9,000 Interview Questions & Answers in an eBook.




Get it now !!
Send your Resume to 6000 Companies

Search Interview Questions

Question: What are the advantages and disadvantages of primary key and foreign key in SQL?

Answer: Primary key

Advantages

1) It is a unique key on which all the other candidate keys are functionally dependent

Disadvantage

1) There can be more than one keys on which all the other attributes are dependent on.

Foreign Key

Advantage

1)It allows refrencing another table using the primary key for the other table



Category SQL Interview Questions & Answers - Exam Mode / Learning Mode
Rating (1.0) By 448 users
Added on 7/25/2011
Views 5085
Rate it!
Question: What are the advantages and disadvantages of primary key and foreign key in SQL?


Answer:

Primary key

Advantages

1) It is a unique key on which all the other candidate keys are functionally dependent

Disadvantage

1) There can be more than one keys on which all the other attributes are dependent on.

Foreign Key

Advantage

1)It allows refrencing another table using the primary key for the other table
Source: CoolInterview.com


First do remember that a table can have only 1 primary key, though we can have many columns with a single primary key, called composite primary key.
Advantages
1. It prevents to enter null data.
2. It prevents to enter duplicate data.
3. It helps to force integrety constraints.





Disadvantage :
On primary key index will be created so during updation of table index need to be adjusted accordingly. this process makes the updation slower Source: CoolInterview.com

Answered by: RISHI RAWAT | Date: 4/10/2009 | Contact RISHI RAWAT Contact RISHI RAWAT


If you have the better answer, then send it to us. We will display your answer after the approval

Rules to Post Answers in CoolInterview.com:-

  • There should not be any Spelling Mistakes.
  • There should not be any Gramatical Errors.
  • Answers must not contain any bad words.
  • Answers should not be the repeat of same answer, already approved.
  • Answer should be complete in itself.

Post your answer here

Inform me about updated answers to this question.
Related Questions
View Answer
What is the wildcard character in SQL?
View Answer
Which is the subset of SQL commands used to manipulate Oracle Database structures, including tables?
View Answer
What operator performs pattern matching?
View Answer
What operator tests column for the absence of data?
View Answer
Which command executes the contents of a specified file?
View Answer
What is the parameter substitution symbol used with INSERT INTO command?
View Answer
Which command displays the SQL command in the SQL buffer, and then executes it?
View Answer
What are the wildcards used for pattern matching.
View Answer
State true or false. EXISTS, SOME, ANY are operators in SQL.
View Answer
State true or false.
!=,
<>,
^=
all denote the same operation.
View Answer
What are the privileges that can be granted on a table by a user to others?
View Answer
What command is used to get back the privileges offered by the GRANT command?
View Answer
Which system tables contain information on privileges granted and privileges obtained?
View Answer
Which system table contains information on constraints on all the tables created?
View Answer
TRUNCATE TABLE EMP;
DELETE FROM EMP;
Will the outputs of the above two commands differ?
View Answer
What is the difference between TRUNCATE and DELETE commands?
View Answer
What command is used to create a table by copying the structure of another table?
View Answer
What will be the output of the following query?
SELECT REPLACE(TRANSLATE(LTRIM(RTRIM('!! ATHEN !!','!'), '!'), 'AN', '**'),'*','TROUBLE') FROM DUAL;
View Answer
What will be the output of the following query?
SELECT DECODE(TRANSLATE('A','1234567890','1111111111'), '1','YES', 'NO' );
View Answer
What does the following query do?
SELECT SAL + NVL(COMM,0) FROM EMP;
View Answer

Please Note: We keep on updating better answers to this site. In case you are looking for Jobs, Pls Click Here Vyoms.com - Best Freshers & Experienced Jobs Website.

View All SQL Interview Questions & Answers - Exam Mode / Learning Mode




India News Network
Latest 20 Questions
Payment of time- barred debt is: (a) Valid (b) Void (c) Illegal (d) Voidable
Consideration is defined in the Indian Contract Act,1872 in: (a) Section 2(f) (b) Section 2(e) (c) Section 2(g) (d) Section 2(d)
Which of the following is not an exception to the rule, "No consideration, No contract": (a) Natural love and affection (b) Compensation for involuntary services (c) Completed gift (d) Agency
Consideration must move at the desire of: (a) The promisor (b) The promisee (c) The promisor or any other party (d) Both the promisor and the promisee
An offer which is open for acceptance over a period of time is: (a) Cross Offer (b) Counter Offer (c) Standing Offer (d) Implied Offer
Specific offer can be communicated to__________ (a) All the parties of contract (b) General public in universe (c) Specific person (d) None of the above
_________ amounts to rejection of the original offer. (a) Cross offer (b) Special offer (c) Standing offer (d) Counter offer
A advertises to sell his old car by advertising in a newspaper. This offer is caleed: (a) General Offer (b) Special Offer (c) Continuing Offer (d) None of the above
In case a counter offer is made, the original offer stands: (a) Rejected (b) Accepted automatically (c) Accepted subject to certain modifications and variations (d) None of the above
In case of unenforceable contract having some technical defect, parties (a) Can sue upon it (b) Cannot sue upon it (c) Should consider it to be illegal (d) None of the above
If entire specified goods is perished before entering into contract of sale, the contract is (a) Valid (b) Void (c) Voidable (d) Cancelled
______________ contracts are also caled contracts with executed consideration. (a) Unilateral (b) Completed (c) Bilateral (d) Executory
A offers B to supply books @ Rs 100 each but B accepts the same with condition of 10% discount. This is a case of (a) Counter Offer (b) Cross Offer (c) Specific Offer (d) General Offer
_____________ is a game of chance. (a) Conditional Contract (b) Contingent Contract (c) Wagering Contract (d) Quasi Contract
There is no binding contract in case of _______ as one's offer cannot be constructed as acceptance (a) Cross Offer (b) Standing Offer (c) Counter Offer (d) Special Offer
An offer is made with an intention to have negotiation from other party. This type of offer is: (a) Invitation to offer (b) Valid offer (c) Voidable (d) None of the above
When an offer is made to the world at large, it is ____________ offer. (a) Counter (b) Special (c) General (d) None of the above
Implied contract even if not in writing or express words is perfectly _______________ if all the conditions are satisfied:- (a) Void (b) Voidable (c) Valid (d) Illegal
A specific offer can be accepted by ___________. (a) Any person (b) Any friend to offeror (c) The person to whom it is made (d) Any friend of offeree
An agreement toput a fire on a person's car is a ______: (a) Legal (b) Voidable (c) Valid (d) Illegal
Cache = 0.015625 Seconds