@echo off
for /f “tokens=1″ %%i in (‘date /t’) do set thedate=%%i

set mm=%thedate:~3,2%
set dd=%thedate:~0,2%
set yyyy=%thedate:~6,4%
echo.
echo.
echo Today : %dd%.%mm%.%yyyy%
echo.

set /A dd=%dd% – 1
set /A mm=%mm% + 0
if /I %dd% GTR 0 goto DONE
set /A mm=%mm% – 1
if /I %mm% GTR 0 goto ADJUSTDAY
set /A mm=12
set /A yyyy=%yyyy% – 1
:ADJUSTDAY
if %mm%==1 goto SET31
if %mm%==2 goto LEAPCHK
if %mm%==3 goto SET31
if %mm%==4 goto SET30
if %mm%==5 goto SET31
if %mm%==6 goto SET30
if %mm%==7 goto SET31
if %mm%==8 goto SET31
if %mm%==9 goto SET30
if %mm%==10 goto SET31
if %mm%==11 goto SET30
if %mm%==12 goto SET31
goto ERROR
:SET31
set /A dd=31 + %dd%
goto DONE
:SET30
set /A dd=30 + %dd%
goto DONE
:LEAPCHK
set /A tt=%yyyy% %% 4
if not %tt%==0 goto SET28
set /A tt=%yyyy% %% 100
if not %tt%==0 goto SET29
set /A tt=%yyyy% %% 400
if %tt%==0 goto SET29
:SET28
set /A dd=28 + %dd%
goto DONE
:SET29
set /A dd=29 + %dd%
: DONE
if /i %dd% LSS 10 set dd=0%dd%
if /I %mm% LSS 10 set mm=0%mm%
set YESTERDAY=%dd%.%mm%.%yyyy%
echo.
echo YESTERDAY : %YESTERDAY%
echo.
echo.
pause

SQL is English like data base query language initially developed by Donald D Chamberlin and Raymond Boyce to manipulate data in IBM’s database called System R. Foreseeing the scope of SQL, Oracle built their SQL based RDBMS and has done much modification to the structure of SQL. Later ANSI (American National Standards Institute) has approved SQL as the standard query language for Relational Databases.

The strengths of SQL provide benefits for all types of users, including application programmers, database administrators, managers, and end users. Technically speaking, SQL is a data sublanguage. The purpose of SQL is to provide an interface to a relational database such as Oracle Database, and all SQL statements are instructions to the database. In this SQL differs from general-purpose programming languages like C and BASIC.

SQL provides statements for a variety of tasks, such as

1. Querying data
2. Inserting, updating, and deleting rows in a table
3. Creating, replacing, altering, and dropping objects
4. Controlling access to the database and its objects
5. Guaranteeing database consistency and integrity

Basic Elements of Oracle SQL

We will see the basic building blocks of SQL Statements. A detailed analysis of these will be included in the later sessions as and when the use of those is required. Those include

1. Datatypes
2. Literals
3. Format Models
4. Nulls
5. Comments
6. Database Objects
7. Schema Object Names

Datatypes

In the previous chapter, we have discussed about the datatypes. The datatype of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one datatype differently from values of another.

Literals

The term Literal refers to a fixed data value. For eg, from our table ‘Scott’, ‘Peter’ are character literals. All character literals should be enclosed in single quotation marks. This helps SQL to identify our data literal from Oracle Keywords and Reserved Words (We will talk about Reserved Words in a later stage). The values like 101, 102 (EMPID) are numeric literals which need not to be enclosed in single quotation marks.  Date related data is called Date Literals.

Format Models

A format model is a character literal that describes the format of datetime or numeric data stored in a character string. A format model does not change the internal representation of the value in the database. When you convert a character string into a date or number, a format model determines how Oracle Database interprets the string.  (More about format models will be discussed later in the data conversion lessons)

Nulls

If a column in a row has no value, then the column is said to be null, or to contain null. Nulls can appear in columns of any datatype that are not restricted by NOT NULL or PRIMARY KEY integrity constraints. Use a null when the actual value is not known or when a value would not be meaningful. (Constraints will be discussed later).

Null values are not equal to zero and therefore do not use null to represent a value of zero.

Comments

Comments are used to denote the description of a particular SQL statement and are separated from its execution. It is not the part of an SQL Statement. These help developers to identify more about an object or a statement.

Database Objects

Oracle Database recognizes objects that are associated with a particular schema and objects that are not associated with a particular schema, as described in the sections that follow.

• Schema Objects

A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include the following types of objects:

• Clusters
• Constraints
• Database links
• Database triggers
• Dimensions
• External procedure libraries
• Index-organized tables
• Indexes
• Index types
• Java classes, Java resources, Java sources
• Materialized views
• Materialized view logs
• Object tables
• Object types
• Object views
• Operators
• Packages
• Sequences
• Stored functions, stored procedures
• Synonyms
• Tables
• Views

Schema Object Names and Qualifiers

Some schema objects are made up of parts that you can or must name, such as the columns in a table or view, index and table partitions and subpartitions, integrity constraints on a table, and objects that are stored within a package, including procedures and stored functions.

There are schema object naming conventions and rules which will be discussed later.

Next chapter we will begin with SQL Statements.

echo off

set /p file= Type your file name :

for /f “tokens=4 ” %%a in (‘dir /a-d/-c %file% ^| findstr /e %file%’) do set size=%%a

set /a KB=(%size%/1024)

echo %KB% KB

set /a MB=(%size%/1024)/1024

Echo %MB% MB

pause

Any application software picks data from its database. A database can be defined as a collection of processed data arranged in two-dimensional tables ( ie . in rows and columns). To manage the stored data, we need specialized software which can be called as Database Management Systems (DBMS).

DBMS arranges and stores data in a logical fashion so that it can be easily maintained. IBM was the first company to introduce a formal database management system called IMS. In 1970, the concept of Relational Structure of a database came into effect which is proposed by Dr. Edgar F Codd.

Earlier, list-model database was used, where data is stored in the form of lists. The maintenance of these list based databases was quite difficult.

Codd’s idea of storing data in a tabular manner started a revolution in the database management systems. Instead of storing the entire data in a list, Codd’s way of tabular storage used a method of splitting the data in a logical fashion and stored in multiple tables and linking the tables together by relating the tables. DBMS which store data in this model is known as RDBMS (Relational Database Management System).

In this modern world we have many RDBMS software ex: Oracle, MS SQL Server, IBM DB2 etc..

In our session we are learning a little about Oracle Database and programming using Oracle. Oracle is the world’s leading RDBMS found by Dr. Larry Ellison based on the relational database structure designed by Dr. E F Codd. Oracle stores data in the form of tables and views. We are not going deep into how oracle stores data, oracle architecture, memory etc… We will go through the details of tables, views etc…

A table in an Oracle database is arranged in a two dimensional way represented by Rows and Columns. It is very much similar to an excel worksheet. The picture below displays the structure of a table.

Employees

The above displays the employee details of an organization. The table has a name, Employees. (It is recommended that while creating the table names, the name should be plural). Each column in the table has a column name such as EMPID, EMPNAME etc. Under each column, similar type of data is stored. Each row contains multiple details of a single entity.

Let us see another table called Departments below. Instead of including the department details of each employee in the same employee table, another table is created to store those. We can see that there is a relation exists between each table in the form of EMPID and DEPTID by which each row of these tables corresponds to each other. And this is how a relational database management systems records data. (The table structure here only for illustration purpose, more about creating a table in correct way will be discussed later).

Department

The data in the above tables can anytime be queried, manipulated by a database query language. Before we start with the database query language, let us analyze some aspects and foundation stones of database. We shall talk about the data types, character sets, operators, and oracle database specific items.

In a typical database, we store different kinds of data in the form of numbers, alphabets, pictures, movie files etc. When you create a table or cluster, you must specify a data type for the columns accordingly.

Oracle Database provides a number of built-in data types as well as several categories of user-defined types that can be used as data types. A datatype can be either scalar or nonscalar. A scalar type contains an atomic value, whereas a non-scalar (sometimes called a “collection”) contains a set of values. A large object (LOB) is a special form of scalar datatype representing a large scalar value of binary or character data. LOBs are subject to some restrictions that do not affect other scalar types because of their size. The below table lists the most common datatypes used in oracle database.

Oracle database also has supplied datatypes for advanced uses. Some of them are CLOB, NCLOB, BFILE, BLOB, RAW, ROWID, LONG RAW, BOOLEAN, EXCEPTION, BINARY FLOAT, BINARY DOUBLE, INTERVAL etc… We will go through each of them in later sessions.

The data types are classified into two:

Character datatype which is used to store character based data

Non-character datatypes which is used to stored number form of data.

In the above tables, we see that each column has its own specific data types. The first column EMPID stores only numbers and therefore NUMBER datatype is used and it allows only numbers to be stored. The second column EMPNAME stores characters, therefore VARCHAR2 datatype is stored which allows alphanumeric characters to be stored. HIREDATE uses DATE datatype and only date format is allowed. Each column has a specification in the form of how many characters can be accommodated maximum.

Next lesion, we will discuss about the database query language which is known as Structured Query Language (SQL).

Next Session will discuss about software and programming technologies.

Microsoft SQL Server Express Is a freely downloadable and distributable product from Microsoft. It is a light weight version of SQL server. SQL Server Express includes powerful features such as SQL Server Management Studio Express, for easily managing a database.

It is mainly for developers, embedded and smaller-scale applications,  You can Create databases up to 4 GB in size. Also there is a hardware utilization limit, we can use only Single physical CPU (multiple cores) and it is only use 1Gb Ram even if you have more than 1GM RAM in your server.  SQL server Express with full compatibility so that you can Transfer any database created in SQL Express to other editions of SQL Server 2008. It is offering high data security for the databases.

Try it Today : Download SQL Server Express 2008.