(1) How do
I list all of my tables?
Ans: SQL>
select * from cat;
(2) Create
one table from another table without copying the data from the first table.?
Ans: SQL> create
table dept_info( dept_id number(10),
2
dept_name varchar(25),
3
constraint pk_dept_id primary key(dept_id)
4 );
SQL> insert into dept_info
values(1,'Account');
SQL> insert into dept_info
values(2,'HR');
SQL> insert into dept_info
values(3,'Payroll');
.SQL> select * from
dept_info;
(3)
How do I select from different user’s tables?
(4)
What is SQL?
Ans:Sql is Structured query
language:
Query:We ask question to get
response
Database understands only
QUERYS and RDBMS is widely used in system n/w.
According to ANSI (American
National Standards Institute), it is the standard language for relational database
management systems.
(5)
What is a function in oracle?
Ans:Function is a subprogram
that returns a single value.we must declare and define before we invoke it
Functions are very powerfull
feature of sql & can be used to (i) perform calculation on data and
modifying individual data items.
Types of Functions:
(i)SINGLE ROW FUNCTION
(ii)MULTIPLE ROW FUNCTION
(iii)Nesting functions
(iv)numeric functions
(v)character or text
functions
(vi)conversion functions
(vii)date
functions
(6) What
is the default format of date in Oracle? How can I change my default date
format?
Ans:The default date format is DD-MON-YY
SQL>select sysdate,systimestamp;
(7)
1)Rollback:
ROLLBACK command execute at the end of current transaction and
undo/undone any changes made since the begin transaction.
Sql>rollback;
2)Savepoint:
SAVEPOINT command save the current point with the unique name in the
processing of a transaction.
Sql>savepoint a;
3) COMMIT:
ANS: COMMIT command to make changes permanent save to a database
during the current transaction.
4) Truncate:
Ans:Removes all rows from a table and rleases the storage
space used by tat table.
Sql>droptable emp1;
5) Delete:
Ans: The DELETE statement is used to delete rows in
a table.
Sql>delete emp1;
6) Drop:
Ans:All data and structure in the table is deleted and any
pending transaction are commited and all indexs are droped
You can’t rollback
the drop table.
Sql>drop column commit;
7) PK:Primary key
Ans:It represents (or) identify each row uniquely in a table,
Only empno is
considered as primary key.
Pk=unique+notnull
Ck=eligible to
become pk
Ak=ck-pk
8) ROUND:
Ans:Rounds value to specified decimal
Round(45.926)à46
9)TRUNC:
Ans:Truncates value to specified decimal
Trunc(45.926)à45
10) Alternate Key:
ANs:Eligible to become to pk but not chosen as pk.
AK=CK-PK
11) Candidate Key:
Ans:It is a relational model of data base and it is eligible
to become PK.
12)Composite key:
Ans: A composite key, in the context of relational
databases,
It is a combination of two or more columns in a
table that can be used to uniquely identify each row in the table
13)Triggers:
Ans:Triggers provide a way of executing PL/SQL code on the
occurrence of specific database
It invokes many
events in table like INSERT,UPDATE,DELETE operations.
14) Equi-Join:
Ans:If we are using “=” operator in join condition is called
equijoin.
Ex:emp.d
ptno=dept.deptno
15)OUTER-JOIN:
Ans:It displays both matched and non matching
(i)full outer,left
outer,Right outer.
16) What is a view? What are its advantages?
Ans: the ability to see something or to be seen
from a particular place.
Advantages
of views::
View the data without storing the data
into the object.
2. Restict the
view of a table i.e. can hide some of columns in the tables.
Disadvatages:
1. Can
not use DML operations on this.
2. When table
is dropped view becomes inactive.. it depends on the table objects.
17) What is a synonym?
Ans: synonym are alternate name for tables to view other
object in database
Ex:create synonym anyname for scott.emp.
18) What is PL/SQL?
Ans:Procedural language /Structured Query Language.
It works only on
oracle RDBMS
It is the
procedural execution to sql with design features of programming language.
Data manipulation
and Query statements of sql
18) What is an Index? Why it is useful?
Ans: The CREATE
INDEX statement is used to create indexes in tables.
Indexes allow the database application to find data fast; without
reading the whole table.
19) Mention some features of Oracle 9i database.?
Ans:Varchar 2000bytes
Varchar2-4000bytes
No recyclebin
20) Mention some features of Oracle 10g database.
Ans:varchar&varchar2}à4000bytes
Recylebin is
possible.
21) What is the meaning of “i” and “g” in 9i & 10g respectively?
Ans: i means Internet
support
g means Grid technology
g means Grid technology
22) What is the purpose of
joining the tables? Explain different types of Joins.
Ans: An SQL JOIN clause is used
to combine rows from two or more tables, based on a common field between them.
The most common
type of join is: SQL INNER JOIN (simple join). An
SQL INNER JOIN return all rows from multiple tables where the join condition is
met.
Types of joins:
Inner join
Outerjoin
Equi join
Non-equijoin
Self join
23) What are the data types available in Oracle
Ans:Character data type
Numeric datatype
Date dattype
Lob dattype