oracle question and answers

8/6/2019 Oracle Question and Answers

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* it is not case sensitive and not space sensitve language

* it maintains ANSI & ISO standards

What are the benefits of SQL?

1. It is flexible, Powerful and easy to learn.

2. It is a non-procedural language. It

a] Processes set of records rather than just one at a time

and

b] Provides automatic navigation to the data.

3. It provides commands for a variety of tasks including :

a] Querying data

b] Creating,Updating and Replacing objects and Inserting,

Updating and Deleting rows.

4. All RDBMS supports SQL

Thus one can transfer the skills gained with SQL from one

RDBMS to another.

5. Programs written in SQL are portable, they can often be

moved from one database to another with little modification.

What is SQL*PLUS?

SQL*PLUS is a Structured Query Language supported by Oracle. Through this only, we store, retrieve,

edit, enter & run SQL commands and PL/SQL blocks. We can perform calculations , list column

definitions, format query reults in the form of a query. or

SQL*PLUS is the ORACLE database language which includes ANSI standard SQL commands plus

additional commands for accessing data in ORACLE database.

What is PL/SQL?

It is a Procedural Language extension of SQL. It can contain any no of SQL statements integrated with

flow of control statements. Thus it combine the Data Manipulating power of SQL with data processing

power of Procedural language.


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What are the different types of SQL commands?

DDL ( Data definition language )

DML ( Data manipulation language )

TCL ( Transact control language)

Session Control Statements. ( ALTER SESSION, ROLE )

System Control Statements. ( ALTER SYSTEM )

What is A DDL statements?

DDL statements are one catagory of SQL statements. DDL statements define (create) or delete (drop)

database objects.Examples are ceate view, create table, create index,drop table and rename tabl. The

other catagories are DML statements and DCL statements.

What is a DML statements ?

DML statements are one catagory of SQL statements. DML statements, such as select, insert, delete and

update, query and update the actual data. The other catagories are DDL statements and DCL

statements.

What are DCL statements ?

DML statements are one catagory of SQL statements. DCLstatments such as, connect, grant select,grant

update and revoke dba, control access to the data and to the database. The other catagories are DDL

and DML statements.

What is a Transaction ?

It can be defined as a logical unit of work. A transaction is a sequence of SQL statements that ORACLE treats as a single unit. The set of

statements is made permanent with the COMMIT statement. Part or all of a transaction can de

undone with the ROLLBACK statement.

All changes to the database between successive COMMITS and / or ROLLBACK operations are called a

transaction.

What is a Commit ?

COMMIT commits any changes made to the database since the last COMMIT was executed implicitlyor explicitly. WORK is optional and has no effect on usage.

To COMMIT means to make changes to data (inserts,updates and deletes) permanent. beforechanges are stored both the old and new data exists so that changes can be made, or so that the


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