1. SQL Introduction

1. SQL Introduction

Q 1 What is mean Data base?

Data base is a set of data. A data base is collection of data file and programs that manipulate those data file. This is storing two type of information user data and Meta data (data about data).

Q 2 What is mean Table Space?

the database is divided into one or more logical storage units called as table spaces.

Q 3 What is mean Data File?
The table space in an Oracle database consists of one or more physical data files.

Q 4 What is mean Oracle Instance?

A data base instance (also known as server) is a set of memory Structure and background process that access a set of data files.

1) Development instance

2) Test Instance

          3) Production Instance.

  

Q. 5.  What is mean SQL and where does it come from?

ü  Structured Query Language (SQL) is a language that provides an interface to relational database systems.

ü  The proper pronunciation of SQL, and the preferred pronunciation within Oracle Corp, is "sequel" and not "ess cue ell".

ü  SQL is an English like language consisting of commands to store, retrieve, maintain & regulate access to your database.

ü  SQL was developed by IBM in the 1970s for use in System R, and is a de facto standard, as well as an ISO and ANSI standard.

ü  In common usage SQL also encompasses DML (Data Manipulation Language), for INSERTs, UPDATEs, DELETEs and DDL (Data Definition Language), used for creating and modifying tables and other database structures.

ü  The development of SQL is governed by standards. A major revision to the SQL standard was completed in 1992, called SQL2. SQL3 support object extensions and are (partially?) implemented in Oracle8 and 9i.

Example SQL statements:

1)  Create table table_name 

    (column_name1 number,  column_name2 varchar2(30));

2)  Insert into table_name values (1, 'xyz');

3) Select * from table_name where column_name2 = 'xyz';

Q.6. which structure can you implement for the database to speed up table reads?

Follow the rules of DB tuning we have to: 

ü  Properly use indexes (different types of indexes)

ü  Properly locate different DB objects across different table spaces, files and so on..

ü  Create a special space (table space) to locate some of the data with special data type ( for example CLOB, LOB and …)