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SQL Interview Questions & Answers - Learning Mode

SQL Interview Questions & Answers - Learning Mode

SQL (pronounced "ess-que-el") stands for Structured Query Language. SQL is used to communicate with a database. According to ANSI (American National Standards Institute), it is the standard language for relational database management systems. SQL consists of a data definition language, data manipulation language, and Data Control Language. The scope of SQL includes data insert, query, update and delete, schema creation and modification, and data access control. Although SQL is often described as, and to a great extent is, a declarative language (4GL), it also includes procedural elements.

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SQL Interview Questions & Answers - Learning Mode
Try SQL Interview Questions & Answers - Exam Mode
Question: What is the use of CASCADE CONSTRAINTS?

Answer: When this clause is used with the DROP command, a parent table can be dropped even when a child table exists. Source:
Question: What is the output of the following query

Answer: 1200. Source:
Question: Why does the following command give a compilation error?

Answer: Variable names should start with an alphabet. Here the table name starts with an '&' symbol. Source:
Question: What are the advantages and disadvantages of primary key and foreign key in SQL?

Answer: Primary key


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


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

Foreign Key


1)It allows refrencing another table using the primary key for the other table
Question: what is the difference between replace and translate functions?

Answer: I Think here we r discussing abt SQL.Replace function is used to replace a string as well as character to another string or character,Translate function exists in ORACLE for translating single character to some other character........ Source:
Question: What is the difference between TRUNCATE and DELETE commands?

Answer: TRUNCATE is a DDL command whereas DELETE is a DML command. Hence DELETE operation can be rolled back, but TRUNCATE operation cannot be rolled back.<br>WHERE clause can be used with DELETE and not with TRUNCATE. Source:
Question: How we get second highest salary in
database. Please show me this coding.

Answer: select top 1 from (select top 2 from (select salary from employee order by salary) order by salary dsc) Source:
Question: What is the difference between cross product & Cartesian product?

Answer: There is no difference between Cartesian product and cross join.
although there syntax are different but they work as a same.

Cartesian or cross product selects all rows from both the table.

tableA 6 rows
tableB 6 rows

Cartesian or cross product
36 rows.
Question: How can i hide a particular table name of our schema.

Answer: you can hide the table name by creating synonyms.

e.g) you can create a synonym y for table x

create synonym y for x;
Question: What will be the output of the following query?
SELECT DECODE(TRANSLATE('A','1234567890','1111111111'), '1','YES', 'NO' );

Answer: NO.
Explanation :
The query checks whether a given string is a numerical digit. Source:
Question: State true or false.
all denote the same operation.

Answer: True. Source:
Question: What does the following query do?

Answer: This displays the total salary of all employees. The null values in the commission column will be replaced by 0 and added to salary. Source:
Question: Difference between decode and case.
in which case we are using case and in which case we are using decode?
with an example.

Answer: First I will give one example using 'decode'


I have used the decode function on 'deptno' column. It will give the user-friendly output. instead of using 'accounting', 'research'.. We can use anything we want to get the friendly outputs.

I have to check-out the ' Source:
Question: How to delete same id in rows?
For example empid=5 repeated for times in rows. How to delete which sql query is used?

Answer: we can use distinct clause for this type of query.distinct clause is used to remove duplicates from table
select rowid distinct from table name
Question: What will be the output of the following query?

Question: Which date function is used to find the difference between two dates?

Answer: MONTHS_BETWEEN. Source:
Question: Difference between Stored Procedure and Trigger

Answer: Information related to Stored procedure you can see in USER_SOURCE,USER_OBJECTS(current user) tables.

Information related to triggers stored in USER_SOURCE,USER_TRIGGERS (current user) Tables.

Stored procedure can't be inactive but trigger can be Inactive.
Question: What command is used to create a table by copying the structure of another table?

Answer: CREATE TABLE .. AS SELECT command
To copy only the structure, the WHERE clause of the SELECT command should contain a FALSE statement as in the following.
If the WHERE condition is true, then all the rows or rows satisfying the condition will be copied to the new table. Source:
Question: What is the difference between file server and a database server ?

Answer: A file server just transfers all the data requested by all its client and the client processes the data while a database server runs the query and sends only the query output. Source:
Question: What is a default TCP/IP socket assigned for SQL Server?

Answer: 1433 is default tcp/ip socket sql server. Source:

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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
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