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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: 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 is the output of the following query

Answer: 1200. 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: 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 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: 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: 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
Will the outputs of the above two commands differ?

Answer: Both will result in deleting all the rows in the table EMP.. 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: 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 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: 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 to find out the 10th highest salary in SQL query?

Answer: Table - Tbl_Test_Salary
Column - int_salary

select max(int_salary)
from Tbl_Test_Salary
where int_salary in
(select top 10 int_Salary from Tbl_Test_Salary order by int_salary)
Question: Which command executes the contents of a specified file?

Answer: START <filename> or @<filename>. Source:
Question: What are the wildcards used for pattern matching.

Answer: _ for single character substitution and % for multi-character substitution. Source:
Question: Which is the subset of SQL commands used to manipulate Oracle Database structures, including tables?

Answer: Data Definition Language (DDL). Source:
Question: What is normalization and different kinds of normalization?

Answer: It is set of rules that have been established to aid in the design of tables that are meant to
be connected through relationships. This set of rules is known as Normalization.
Benefits of normalizing your database will include:
√ Avoiding repetitive entries
√ Reducing required storage space
√ Preventing the need to restructure existing tables to accommodate new data.
√ Increased speed and flexibility of queries, sorts, and summaries. Source:
Question: What is the use of the DROP option in the ALTER TABLE command?

Answer: It is used to drop constraints specified on the table. Source:
Question: What is the difference between where condition and having condition?

Answer: When we use WHERE clause with the GROUP BY ALL clause,it displays all groups including those excluded from the WHERE clause whereas the HAVING clause,if used with the GROUP BY ALL clause overrides the functionality of the ALL Clause and displays only those groups that meet the condition specified in the HAVING clause. 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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