Define PL/SQL sequences and write syntax for a sequence

Correct Answer: A package is a collection of related PL/SQL objects The package contains a body and a specification The package specification has the declaration which is public and can be used in the PL/SQL sub programs inside the package The package body holds the implementation of all the PL/SQL objects declared in the specification Example of a PL/SQL Package CREATE OR REPLACE PACKAGE emp_data AS PROCEDURE add_employee ( ename VARCHAR2, job VARCHAR2, mgr NUMBER, sal NUMBER, deptno NUMBER); END emp_actions; CREATE OR REPLACE PACKAGE BODY emp_data AS PROCEDURE add_employee ( ename VARCHAR2, job VARCHAR2, mgr NUMBER, sal NUMBER, deptno NUMBER) IS BEGIN INSERT INTO emp VALUES (empno_seqNEXTVAL, ename, job, mgr, SYSDATE, comm, deptno); END add_employee; END emp_data; Advantages of PL/SQL packages : Packages are easier for application designing, encapsulating data, additional functionality and better performance An application has various modules which can be placed in packages and handled easier

Correct Answer: PL/SQL exceptions are raised using the RAISE command This command is used when exceptions are defined by programmer and not implicit exceptions Example: Declare and raising an exception: DECLARE short_of_attendance EXCEPTION; min_attendance NUMBER(4); BEGIN IF min_attendance < 10 THEN RAISE short_of_attendance; END IF; EXCEPTION WHEN short_of_attendance THEN -- handle the error END;

Correct Answer: 1)Divide by zero ? This is raised when any number is attempted to divide by zero 2)TOO MANY ROWS - A SELECT INTO statement returns more than one row 3)CASE_NOT_FOUND - No choice in the WHEN clause of a case statement is selected 4)LOGIN_DENIED - An attempt to login with an invalid username or password 5)PROGRAM_ERROR - An internal PL/SQL problem

Correct Answer: - %FOUND This is a Boolean variable which evaluates to TRUE if the last row is successfully fetched - %NOTFOUND This is a Boolean variable which evaluates to TRUE if the last row is not successfully fetched This means there are no more rows to fetch - %ROWCOUNT Returns the number of rows fetched by the cursor - %ISOPEN If the cursor is open, it evaluates to TRUE else FALSE

Correct Answer: A record data type represents a data type for that row in a database table It lets u define your own records and not your own fields

Correct Answer: The CACHE option means how many sequences will be stored in memory for access by the application objects The performance is faster However in case of the database is down the data is memory is lost for the sequence The NO CACHE option means values are not stored in memory So there might be some performance issue

Correct Answer: An index is a object which is used to improve performance during retrieval of records CREATE [UNIQUE] INDEX index_name ON employee[emp_id, emp_name,dept_id] [COMPUTE STATISTICS] The UNIQUE keyword is used when combined values of the index should be unique The COMPUTE STATISTICS during the creation of index optimizes the plan of execution of the SQL statement and improves performance

Correct Answer: We need to first login to the data base as: SQLPLUS followed by user_name/password Then we need to execute the following query: CREATE USER user_name IDENTIFIED BY abcd; in this query a user_name suggest the user that is created which has a password abcd which is required for login in database

Correct Answer: The following are the areas of concern for tuning: - Memory Usage - Data Storage - Data Manipulation - Physical Storage - Logic Storage - Network Traffic Tuning Memory Usage: In Oracle 10g, we can use the Automatic Workload Repository (AWR) toolset to gather and manage statistical data but in case of Oracle 11g, we can use new initialization parameters such as MEMORY_TARGET to further control the overall memory used by Oracle It helps us to tune the database automatically when we don?t have time to read the AWR report Tuning Data Manipulation: There are two ways to tune Data manipulation in Oracle one way is through Conventional Path mode and second is Direct Path mode Tuning Physical Storage: We need to tune the physical storage because it limits the disk in database This can be done by: Distributing I/O, Striping and Mirroring

Correct Answer: Basic Replication : Basic replication is implemented using standard CREATE SNAPSHOT or CREATE MATERIALIZED VIEW statements It can only replicate data and not procedures, indexes replication is always one-way, and snapshot copies are read only Advanced Replication : Advanced replication supports various configurations of updatable snapshot, multi-master and update anywhere replication It is more difficult to configure but allows data and other database objects like indexes and procedures to be replicated Differences between Basic and Advanced replications: - With basic replication, data replicas provide read-only access to the table data whereas advanced replication features extend the capabilities of basic read-only replication by allowing applications to update table replicas throughout a replicated database system - With Basic Replication applications can query data from local data replicas On the other hand with advanced replication, data replicas anywhere in the system can provide both read and update access to a table's data