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Oracle Interview Questions and Answers
What is a Check Box?
A Check Box is a two state control that indicates
whether a certain condition or value is on or off, true
or false. The display state of a check box is always
either "checked" or "unchecked".
What is a canvas-view?
A canvas-view is the background object on which you
layout the interface items (text-items, check boxes,
radio groups, and so on.) and boilerplate objects that
operators see and interact with as they run your form.
At run-time, operators can see only those items that
have been assigned to a specific canvas. Each canvas, in
term, must be displayed in a specific window.
Explain the following file extension related to library?
.pll,.lib,.pld
The library pll files is a portable design file
comparable to an fmb form file
The library lib file is a plat form specific, generated
library file comparable to a fmx form file
The pld file is Txt format file and can be used for
source controlling your library files Parameter
Explain the usage of WHERE CURRENT OF clause in cursors
?
WHERE CURRENT OF clause in an UPDATE,DELETE statement
refers to the latest row fetched from a cursor. Database
Triggers
Name the tables where characteristics of Package,
procedure and functions are stored ?
User_objects, User_Source and User_error.
Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and
Explicit Cursor. PL/SQL uses Implicit Cursors for
queries. User defined cursors are called Explicit
Cursors. They can be declared and used.
What are two parts of package ?
The two parts of package are PACKAGE SPECIFICATION &
PACKAGE BODY. Package Specification contains
declarations that are global to the packages and local
to the schema. Package Body contains actual procedures
and local declaration of the procedures and cursor
declarations.
What are two virtual tables available during database
trigger execution ?
The table columns are referred as OLD.column_name and
NEW.column_name.
For triggers related to INSERT only NEW.column_name
values only available.
For triggers related to UPDATE only OLD.column_name
NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name
values only available.
What is Fine Grained Auditing? (for DBA)
Fine Grained Auditing (DBMS_FGA) allows auditing records
to be generated when certain rows are selected from a
table. A list of defined policies can be obtained from
DBA_AUDIT_POLICIES. Audit records are stored in
DBA_FGA_AUDIT_TRAIL. Look at this example:
o Add policy on table with autiting condition...
execute dbms_fga.add_policy('HR', 'EMP', 'policy1', 'deptno
> 10');
o Must ANALYZE, this feature works with CBO (Cost Based
Optimizer)
analyze table EMP compute statistics;
select * from EMP where c1 = 11; -- Will trigger
auditing
select * from EMP where c1 = 09; -- No auditing
o Now we can see the statments that triggered the
auditing condition...
select sqltext from sys.fga_log$;
delete from sys.fga_log$;
What is a package ? What are the advantages of packages
? What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the complier to
associate an exception with an oracle error. To get an
error message of a specific oracle error. e.g. PRAGMA
EXCEPTION_INIT (exception name, oracle error number)
What is a Virtual Private Database? (for DBA)
Oracle 8i introduced the notion of a Virtual Private
Database (VPD). A VPD offers Fine-Grained Access Control
(FGAC) for secure separation of data. This ensures that
users only have access to data that pertains to them.
Using this option, one could even store multiple
companies' data within the same schema, without them
knowing about it. VPD configuration is done via the
DBMS_RLS (Row Level Security) package. Select from
SYS.V$VPD_POLICY to see existing VPD configuration.
What is Raise_application_error ?
Raise_application_error is a procedure of package
DBMS_STANDARD which allows to issue an user_defined
error messages from stored sub-program or database
trigger.
What is Oracle Label Security? (for DBA)
Oracle Label Security (formerly called Trusted Oracle
MLS RDBMS) uses the VPD (Virtual Private Database)
feature of Oracle8i to implement row level security.
Access to rows are restricted according to a user's
security sensitivity tag or label. Oracle Label Security
is configured, controlled and managed from the Policy
Manager, an Enterprise Manager-based GUI utility.
Give the structure of the procedure ?
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
What is OEM (Oracle Enterprise Manager)? (for DBA)
OEM is a set of systems management tools provided by
Oracle Corporation for managing the Oracle environment.
It provides tools to monitor the Oracle environment and
automate tasks (both one-time and repetitive in nature)
to take database administration a step closer to "Lights
Out" management.
Question What is PL/SQL ?
PL/SQL is a procedural language that has both
interactive SQL and procedural programming language
constructs such as iteration, conditional branching.
What are the components of OEM? (for DBA)
Oracle Enterprise Manager (OEM) has the following
components:
. Management Server (OMS): Middle tier server that
handles communication with the intelligent agents. The
OEM Console connects to the management server to monitor
and configure the Oracle enterprise.
. Console: This is a graphical interface from where one
can schedule jobs, events, and monitor the database. The
console can be opened from a Windows workstation, Unix
XTerm (oemapp command) or Web browser session (oem_webstage).
. Intelligent Agent (OIA): The OIA runs on the target
database and takes care of the execution of jobs and
events scheduled through the Console.
What happens if a procedure that updates a column of
table X is called in a database trigger of the same
table ?
Mutation of table occurs.
Is it possible to use Transaction control Statements
such a ROLLBACK or COMMIT in Database Trigger ? Why ?
It is not possible. As triggers are defined for each
table, if you use COMMIT of ROLLBACK in a trigger, it
affects logical transaction processing.
How many types of database triggers can be specified on
a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger
for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according
to the returned Boolean value.
What are the modes of parameters that can be passed to a
procedure ?
IN,OUT,IN-OUT parameters.
Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
Write the order of precedence for validation of a column
in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.?
I & ii.
Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
Explain how procedures and functions are called in a
PL/SQL block ?
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability
and one time compilation.
What is an Exception ? What are types of Exception ?
Exception is the error handling part of PL/SQL block.
The types are Predefined and user defined. Some of
Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
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