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Any Languages in Dot Net Framework

2010-01-09T10:47:00.000+08:00

The beauty in Dot Net Framework is that, you can use whatever language you like to develop your application. For example, if you're a VB people, you can use VB.Net or you can use J# if you're a Java people (Even though the syntax is not exactly the same, but you can catch up faster). Below are some language that Dot Net Framework supports:

C#: this should be the genuine language in Dot Net Framework
VB.Net: influenced by Visual Basic
J#: influenced by Java
F#: influenced by Lambda Expression
Boo: influenced by Python
IronPython: influenced by Python also
IronRuby: influenced by Ruby

Dot Net Framework can do this by using the Common Language Runtime (CLR). Whatever language you compiled will convert into Common Intermediate Language (CIL) and executed by CLR.

If you have installed Dot Net Framework SDK, you can find a tools called Microsoft Intermediate Language Disassembler (MSIL Disassembler ). Using this tool allow you to read the CIL in all Dot Net compiled assemblies (either it is an executable file or library).

Difference between Linux and Windows (and similarity)

2009-11-01T10:03:00.000+08:00

Linux, Mac, Solaris, BSD and some other OS share the same origin, grandfather UNIX, which make them having similar command and file structure. While Windows stands as its owned, has its owned unique command and structure that different from the UNIX bloodline. However all the OS are actually serve the same purpose, just that in different methods:

File System Type: this is the type of method on how to format the hard disk. Currently Windows cannot browse hard disk (or partition) of Linux file system, however newer Linux can browse (or even modify) Windows file system.

Windows: FAT and NTFS
Linux: EXT2, EXT3 and EXT4

File Structure: this is another thing that make Windows user confuse on Linux. In Windows, the file structure is based on hard disk, and then each hard disk can have more than 1 partition. For example C:\ is the hard disk and D:\ may be the second partition of the hard disk. However Linux treats hard disk and partition separately, which the structure will base on partition like /, /home, /etc and others.

Linux /home is equivalent to Windows c:\document and settings
Linux /bin and /sbin is equivalent to Windows c:\windows\system32
Linux /opt is equivalent to Windows c:\program files

Command: of course the commands between Linux and Windows are vary, but you can always find the equivalent command.

List files: ls and dir
Ping: ping (same for both OS)
Change directory: cd (same for both OS)
Make directory: mkdir (same for both OS)
Copy: cp and copy
Move: mv and move
Delete: rm and del

Tomcat configuration file - web.xml

2009-09-26T11:03:00.000+08:00

Tomcat configuration file (web.xml) is using XML pattern, which the global configuration file is within tomcat\conf directory, and individual configuration file is within tomcat\wepapps\webdir\WEB-INF directory. User can always refer to the global configuration file as a sample to set the individual configuration file. The parent node of web.xml is <web-app> and below is the common nodes that can be used:

Description for the web application.
<description> Description for Web Application </description>
Map the servlet to associate class and URL pattern.
<servlet> <servlet-name>servlet name</servlet-name> <servlet-class>class name</servlet-class> </servlet> <servlet-mapping> <servlet-name>servlet name</servlet-name> <url-pattern>url pattern</url-pattern> </servlet-mapping>
Map the taglib to associate TLD files.
<taglib> <taglib-uri> http://www.gnokproject.com/taglibs/taglib-v1.0 </taglib-uri> <taglib-location> /WEB-INF/jsp/taglib.tld </taglib-location> </taglib>
Map extension to associate mime type.
<mime-mapping> <extension>html</extension> <mime-type>text/html</mime-type> </mime-mapping>
Session timeout.
<session-config> <session-timeout>30</session-timeout> </session-config>
First file to be accessed.<welcome-file-list> <welcome-file>index.jsp</welcome-file> <welcome-file>index.html</welcome-file> </welcome-file-list>

WEBAPPS directory structure

2009-09-25T14:49:00.002+08:00

WEPAPPS is the directory that keep all the JSP files and JAVA files, and the place where people will get into when they are accessing Apache Tomcat. Inside WEBAPPS directory, each sub directory represents a sub directory in the URL, for example a sub directory named subdir represents www.gnokproject.com/subdir. Except for one directory called ROOT which represents the root directory www.gnokproject.com.

Inside each sub directory will have a directory called WEB-INF which contain:

classes directory: keep the JAVA source files which will be auto compiled by Tomcat when the classes are needed.
jsp directory: keep the TLD files or the tag library files.
lib directory: keep the JAR files.
web.xml: configuration files of that particular directory.

Apache Tomcat directory structure

2009-09-23T12:59:00.001+08:00

Tomcat's directory structure:

bin: Keep all execution files, for example startup.bat and shutdown.bat.
conf: Keep all the common configuration files, such as server.xml.
lib (in 6.0, or common, server, shared in 5.5): Keep all the common classes and jar files that will be shared by all JAVA and JSP files in webapp.
logs: Keep all the log files.
webapps: Keep all the JSP files, where you normally spend most of the time here.
temp: Temporary directory.
work: Keep the caches compiled from JSP and JAVA files from wepapp.

Change Tomcat port from 8080 to 80

2009-09-23T12:19:00.003+08:00

To change Apache Tomcat port from 8080 to 80 (so that developer or user doesn't need to type :8080 at the back of the URL):

Edit TOMCAT_DIR\conf\server.xml.
Look for line similar to below (the keyword is connector and 8080):
<connector connectiontimeout="20000" port="8080" protocol="HTTP/1.1" redirectport="8443"></connector>
Just change 8080 to 80 and restart Tomcat.

Setup Apache Tomcat to host JSP

2009-09-23T12:03:00.000+08:00

JSP (Java Server Page) is Java based web programming language. Similar to ASP and ASPX (and different from PHP), JSP can be compiled into classes before used in the pages. To start coding in JSP, we need to setup Apache Tomcat first. Follow the steps below:

Download JDK (Java Development Kit) from Java Website. Any version will do, but if you don't have any idea, just download and install the newest version.
Download Apache Tomcat from Apache Tomcat Website. Currently there are versions 4.1, 5.5 and 6.0. Either version will do, or just pick the newest version.
There are 2 types of Tomcat installation file, zip and windows installer. Either type is fine, or just download the zip version. Extract the zip file to any directory.
Go to the Tomcat directory that you extracted (or installed), go to bin folder and edit the startup.bat file.
Add the JAVA_HOME environment variable at the beginning of the startup.bat file (after @echo off)set java_home=C:\Program Files\Java\jdk1.6.0_16
Then you may double click the startup.bat to start Tomcat. If a command terminal is shown without disappearing, it properly means OK.
To test it out, open a browser and go to localhost:8080. If something come out (not the error message of course), that means you have setup Tomcat successfully.

Oracle Net Manager

2009-08-26T08:00:00.001+08:00

Net Manager is an utility come together with Oracle DBMS. User can find it inside Network Administrator at start menu or execute it by using command netmgr. Net Manager serves for 2 main purposes:

Set TNS Name at client PC. TNS name is the connection setting at client PC so that it is able to access database.

Go to the tree navigator, select Service Naming and click add (green plus button at left panel).
Set Net Service Name, what ever name you want.
Set Network Type, which normally TCP/IP.
Set Host Name and Port Number. Host Name you can either use IP address or DNS Name (if you got a DNS server at your network). While the default port is 1521.
Set Service Name and Connection Type. Service Name is the name of the database, while Connection Type we can left it as default.
Done.

Set Listener at Server. Listener is a process to accept connection from client and pass the connection to the database.

Go to the tree navigator, select Listeners and click add (green plus button at left panel).
Set what ever name you want for the listener.
At the top of right panel, you can see a drop down box, which we need to set 2 things: Listening Location and Database Services.
Listening Locations: add new a address, fill in Protocol (TCP/IP), Host (normally localhost will do where listener is resided together with the database) and Port (default 1521).
Database Services: add new database, set Global Database Name and SID (both are the name of database) and Oracle Home Directory (where you install oracle DBMS).

Physical and logical structure of database

2009-08-09T13:40:00.000+08:00

In Oracle, there are 2 types of structure: physical and logical structure.

Physical Structure: it is simply the physical data files that you can see in a file manager. You can find most of them in the directory where your database is resided. Few types of file:
- Data File: extension is DBF, where the data is stored.
- Control File: extension is CTL, where the database current state is stored
- Parameter File: extension is ORA, parameter file of all kind of database process include listener. Usually store in directory where you install your DBMS.
- Redo Log: extension is RDO, store the changes of your database transaction before commit is issued.
Logical Structure: it only stay in memory, where physically store in physical file. It only appear when the database service is started, and only can be view by using certain database tools. Few types of logical structure:
1. Tablespace: where the tables or data are stored. 1 tablespace can map to 1 or more data files.
2. Segment: Smaller unit in tablespace, which can further categorized into data segment, index segment, temporary segment and rollback segment.
3. Extend: Smaller unit in Segment.
4. Block: Smaller unit in Extend.

For Update Option in Select Statement

2009-08-09T13:00:00.000+08:00

You can lock a record by querying it, with this FOR UPDATE option in your select statement:

select * from dept where code = '10' for update;

When other users try to query the same record, it will return a resource busy error. It depends on whether you use FOR UPDATE NOWAIT or FOR UPDATE WAIT.

-- immediate return the error
select * from dept
where code = '10'
for update nowait;

-- try for 3 seconds before return the error
select *
from dept
where code = '10'
for update wait 3;

Using FOR UPDATE SKIP LOCKED option can return those records not locked, instead of returning an error message

select *
from dept
for update skip locked;

Update Cascade and Delete Cascade

2009-08-03T09:40:00.003+08:00

When creating a table with a foreign key, we can add additional option for purpose of update and delete:

create table emp (id number primary key, dept number, constraint fk foreign key (dept) references dept (id) on update cascade)

When you change the id column in dept table, the changes will be propagated to the child table, or in other words the dept column in emp will be changed to the new dept's id as well.

create table emp (id number primary key, dept number, constraint fk foreign key (dept) references dept (id) on delete cascade)

When you delete a record in dept table, the record in emp table that referring to the deleted record will be removed as well.

What is export and import in Oracle?

2009-07-11T12:00:00.000+08:00

Export and Import are two utilities in Oracle database used to extract data from database into a single file, and also extract data from that single file into a database. We normally call that file as dump file. It is widely used during backup and transfer data from one database to another.

Use command below to show out the parameters that can be used in Export:
exp help=y
To export everything in database:
exp [username]/[password]@[database] full=y file=[dump file] log=[log file]
To export everything in one single schema:
exp [username]/[password]@[database] owner=[schema] file=[dump file] log=[log file]
To export particular tables in database:
exp [username]/[password]@[database] tables=([table],[table]) file=[dump file] log=[log file]
To show parameters that can be used in Import:
imp help=y
To import everything in a dump file:
imp [username]/[password]@[database] full=y file=[dump file] log=[log file]
To import particular schema in a dump file:
imp [username]/[password]@[database] fromuser=[schema in dump file] touser=[schema in db] file=[dump file] log=[log file]
To import particular tables in dump file:
imp [username]/[password]@[database] tables=([table],[table]) file=[dump file] log=[log file]
To import table structure only, add the following parameter:
rows=n
To import table (or other objects) that already exist in database, add following parameter:
ignore=y
Normally import the whole database cannot be done in one shot, need to import objects of different type one by one:
imp [username]/[password]@[database] full=y file=[dump file] log=[log file] ignore=y rows=y constraints=n indexes=n grants=n imp [username]/[password]@[database] full=y file=[dump file] log=[log file] ignore=y rows=n constraints=y indexes=n grants=n imp [username]/[password]@[database] full=y file=[dump file] log=[log file] ignore=y rows=n constraints=n indexes=y grants=n imp [username]/[password]@[database] full=y file=[dump file] log=[log file] ignore=y rows=n constraints=n indexes=n grants=y

Cursor and for loop in PL/SQL

2009-07-09T14:00:00.001+08:00

In PL/SQL, we can use method below to query data from database:

select [column] into [variable]
from [table];

However method above can only retrieve one single row of data. To retrieve data more than 1 row, we can use cursor instead. First we need to declare the cursor at the declaration section:
cursor [cursor name] is [select statement];

For example:

cursor c is select id, name
from emp;

Then at the operation section, we can use a special for loop to retrieve the data:

for [row variable] in [cursor name] loop
    do something;
end loop;

For example:

for r in c loop
    insert into temp values (r.id, r.name);
end loop;

Basic PL/SQL: Part 3 (Alternate and Loop)

2009-07-04T09:00:00.001+08:00

IF structure syntax:


if [condition] then
[do something];
elsif [condition] then
[do something];
else
[do something];
end if;

LOOP syntax:


loop
[do something];
exit when (condition);
end loop;

WHILE LOOP syntax:

while (condition) loop
[do something];
end loop;

FOR LOOP syntax:

for [counter] in [start] .. [end] loop
[do something];
end loop;

Basic PL/SQL: Part 2 (Function, Produre and Trigger)

2009-07-04T08:30:00.000+08:00

Syntax to create Function:
CREATE OR REPLACE FUNCTION [function name]([parameter] [IN|OUT] [data type])

RETURN [data type]
AS
 [declare];

BEGIN

[do something];

RETURN [something];

END;

Syntax to create Procedure:
CREATE OR REPLACE PROCEDURE [procedure name]([parameter] [IN|OUT] [data type]) AS

[declaration];

BEGIN

[do something];

END;

Syntax to create Trigger:
CREATE OR REPLACE TRIGGER [trigger name]

[AFTER | BEFORE] [INSERT OR UPDATE OR DELETE] ON [table name]

 REFERENCING NEW AS NEW OLD AS OLD FOR EACH ROW
BEGIN
 IF INSERTING THEN
  [do something];

 END IF;

 IF UPDATING THEN
  [do something];

 END IF;

 IF DELETING THEN
  [do something];

 END IF;
END;
/

Basic PL/SQL: Part 1 (Anonymous)

2009-07-02T09:45:00.000+08:00

SQL is only used to interact with database, and itself cannot be coded in procedural structure (which means no alternate or looping). To solve this weakness, Oracle provides another language called PL/SQL (Procedural Language/Structured Query Language). 4 situations that we can use PL/SQL:

Anonymous, it is written in script form and saved as file, not a database object and cannot pass in any parameters or return any value.
Procedure
Function
Trigger

Basic syntax to write an anonymous PL/SQL:

declare
 [variable name] [data type] := [default value];
begin
 [action to be performed];
exception

 while others then
  [exception handler];
end;
/

For example:


declare
 v_name varchar(50) := '';
begin
 select name into v_name

from emp

 where id = 1;
exception
 while others then
  raise;
end;
/

Functions in Oracle

2009-07-01T16:30:00.001+08:00

Oracle provides some predefined functions that can be used in SQL:

Date function:

months_between(date1, date2), return months between date1 and date2. For example months_between('1/jan/09', '2/feb/09') will return 1.

sysdate will return today's date.

String function:

lpad(str, l, chr), left padding str with chr in length l. For example lpad('1', 3, '0') will return '001'.

rpad(str, l, chr), right padding str with chr in length l. For example rpad('1', 3, '0') will return '100'.

length(str), return the length of str. For example length('1234') will return 4.

substr(str, s, l), return portion of str, start from position s, follow by length l. For example substr('123456', 2, 2) will return 23.

Conversion function:

to_date(str, f), convert str to date in the format of f. For example to_date('1/7/2009', 'dd/mm/yyyy').

to_char(num), convert num to string.

to_number(str), convert str to number.

Group function:

count(c), return number of row where c is the column name.

sum(c), return the sum of value in column c where c should be a numeric column.

max(c), return the maximum value in column c.

min(c), return the minimum value in column c.

Others:

nvl(val, ret), return value of ret if val is null.

decode(val, cond1, ret1, cond2, ret2, ret3), same as:

if (val == cond1) return ret1
else if (val == cond2) return ret2
else return ret3

Data Types in Oracle

2009-07-01T10:30:00.000+08:00

Data types in Oracle:

char(l), is used to store fixed length string where l is the maximum length of the string.
varchar2(l), is used to store variable length string where l is the maxium length of the string. Different of varchar2 and char is that: no matter how long the string store in char, it will reserve space of length defined in char, while varchar2's length can be flexible.
varchar(l), is same as varchar2 but varchar2 have a higher string length capacity.
number(p, s), is used to store either integer or double, where p (precision) is the length of the number and s (scale) is the decimal of the number.
date, is used to store date and time, where the default date time format is dd/mon/yy hh24:mm:ss.
blob is used to store binary object like image, document or audio file. lob is stand for Large Object.
long is used to store string, which has longer capacity than varchar2.
raw is used to store binary object like blob, and actually is obsolete.

Basic SQL: Alter (Part 7)

2009-07-01T09:35:00.000+08:00

Alter statement is used to alter the structure of database objects, and like Create statement, different objects have different syntax. Below are example to alter a table:

Add column:alter table [table name] add [column name] [data type]
Example:alter table temp add test varchar(10);
Remove column:alter table [table name] drop column [column name]
Example:alter table temp drop column test;
Add constraint:alter table [table name] add constraint [constraint name] [constraint type] [constraint details]
Example:alter table temp add constraint temp_uk unique (name);
Remove constraint:alter table [table name] drop constraint [constraint name]
Example:alter table temp drop constraint temp_uk;

To change password of a user, use syntax below:


alter user [user name]
identified by [new password]

Example:


alter user james
identified by new_password;

Basic SQL: Create (Part 6)

2009-06-30T13:30:00.002+08:00

Create statement is used to create database objects, and different objects have different syntax. Below are basic syntax for creating some common database objects:

Create Table:
create table [table name] ( [column name] [data type] [not null], constraint [constraint name] [constraint type] [constraint detail] )

For example:
create table emp ( id number not null, name varchar(50), dept number, salary number(9,2) not null, constraint emp_pk primary key (id), constraint emp_fk foreign key (dept) references dept (id), constraint emp_uq unique (id), constraint emp_chk check (salary >= 0) );
Tips to clone a table:
create table emp_clone as select * from emp;
Create View:
create view [view name] as [select statement]

For example:
create view emp_vu as select * from emp where dept = 'ACCOUNT';
Create User:
create user [user name] identified by [password]

For example:
create user james identified by secret;

Create Synonym:
create [public] synonym [alias] for [database object]

For example:
create public synonym employee for emp;

Basic SQL: Delete (Part 5)

2009-06-30T11:00:00.001+08:00

Delete statement is used to remove existing data from table. Basic syntax is as below:

delete from [table]
where [conditions]

Example:

delete from emp
where id = 1;

Same as Update statement, if where conditions is not set, it will remove all the data in the table.

Basic SQL: Update (Part 4)

2009-06-30T09:50:00.001+08:00

Update statement is used to modify existing records in table. Below is the basic syntax:

update [table]
set [columns] = [value]
where [conditions]

For example:

update emp
set name = 'James Bond',
dept = 'ADMIN'
where id = 1;

Aware that if we didn't put any where condition, the statement will apply the changes to all the records.

Basic SQL: Insert (Part 3)

2009-06-30T09:40:00.003+08:00

Insert statement is used to add new records into table. Below is the basic syntax:

insert into [table] ([columns])
values ([values])

Example for Insert statement:

insert into emp (id, name, dept)
values (1, 'James', 'ACCOUNT');

To insert a batch of records from another table, we can use method below:

insert into table
[select statement]

For example:

insert into emp_account (id, name, dept)
select id, name, dept

from emp
where dept = 'ACCOUNT';

Basic SQL: Select (Part 2)

2009-06-30T09:00:00.002+08:00

Select statement is used to query data from database. Basic syntax is like below:

select [columns as alias]
from [tables as alias]
where [conditions]
group by [columns]
having [group conditions]
order by [columns]

Some example of select statement:

select id as ID, name as "Employee Name", dept as Department
from emp as e
where e.name like '%JAMES%
order by e.id;

select e.id as ID, e.name as "Employee Name", count(*) as Count
from emp as e
group by e.id, e.name
having count(*) > 10;

Some special select statements:

Inner join, where both tables must have the same data.
select e.id, e.name, e.dept, d.name from emp e, dept d where e.dept = d.id;
Or
select e.id, e.name, e.dept, d.name from emp e join dept d on e.dept = d.id;

Outer Join, where both tables might not have the same data.
select e.id, e.name, e.dept, d.name from emp e, dept d where e.dept = d.id(+);
Or
select e.id, e.name, e.dept, d.name from emp e left join dept d on e.dept = d.id;

Inner Query, a select statement within a select statement which technically is a temporary view.
select e.id, e.name, e.dept, d.name from emp e, (select * from dept where name like '%ACCOUNT%') d where e.dept = d.id;

Union, mix two (or more) select statements' result together. Those duplicated records will only show 1 record and columns selected by all the statements must be the same.
select e.id from emp e union select e.id from emp1 e;

Intersect, show only records that exist in both (or more) select statements. Same as Union, duplicated records will only show 1 record and columns selected by all the statements must be the same.
select e.id from emp e intersect select e.id from emp1 e;

Minus, show only records in the first select statement that do not exist in the second statement.
select e.id from emp e minus select i.issueby from invoice i;

Basic SQL (Part 1)

2009-06-30T08:40:00.001+08:00

There are 3 types of SQL statement:

Data Manipulation Language (DML), used to manipulate data in a table. 4 types of DML:
1. Select, used to query data.
2. Insert, used to add new data.
3. Update, used to modify existing data.
4. Delete, used to remove data.
Data Definition Language (DDL), used to manipulate structure of the database objects, which include table, view and others. 3 types of DDL:
1. Create, used to add new database object.
2. Alter, used to modify existing database object structure, for example add column to a table.
3. Drop, used to remove database object.
Transaction Control Language (TCL), used to control the transaction. When user issues the first SQL statement, a transaction will be started and user can decide to end the transaction with either Commit or Rollback.
1. Commit, used to save changes made by user.
2. Rollback, used to undo all the changes made by user.
3. Savepoint, used to make checkpoint for commit or rollback operation.

Objects in database (Part 2)

2009-06-29T15:30:00.001+08:00

Continue on objects in database:

Constraint is rule set in table's columns, where data to be modified must follow. Example of constraint including:

Primary Key, where the column(s) is the identifier of records in the table, must not be null (in Oracle, where there is relational database which allow primary key to be null) and must be unique.
Unique, where data in this column must be unique or no duplicate, but can be null.
Not null, where this column must not be null (null and empty or zero is not the same).
Foreign Key, where data in this column must exist in another table's Primary key.
Check, normally is the user defined constraint, for example this column can only have integer more than 0.

Index is table reference which can make the search of record faster. Index is created based on column(s), and create a primary key will always generate an index based on the key.
Function is a short hand of PL/SQL which can return a value. It can either be used in PL/SQL or inside a SQL statement.
Procedure is also short hand of PL/SQL, which do not return any value. It cannot be used in SQL statement.
Package is collection of functions and procedures. It has 2 parts:

Package specification, where defined which function or procedure can be used by user, or open to public. The body of function and procedure will not be coded in here.
Package body, where all the all the body of function and procedure is coded.

Trigger is event handler of table. For example, we can create a trigger to do something when data is inserted, updated or deleted in a table.
Sequence is code generator for records, and it can only generate integer.

Objects in database (Part 1)

2009-06-29T15:05:00.000+08:00

Objects inside a relational database:

User is the login used to access database. User itself cannot do anything, not even can access to database. It needs to be granted with neccessary privileges in order to access database and perform any operations, for example we need to grant create session privilege to users in order for them to access database and create table privilege for them to create table.
Role is simply a collection of privileges that predefined in the database. For example, if we grant dba role (Database Administrator) to a user, the user can do anything within the rights defined in role dba. We can even create customized role like clerk and grant it to user, so that the user can (and only) access clerk related data.
Schema can be defined as a group with the database objects inside, and in Oracle it is simply the user who created the database objects. For example when user james create a table invoice, this invoice table will be under james schema.
Session is the connection when a user logs into the database.
Table is place where actual data is kept, which formed by column and row. Column is the structure of the table, while row is the record of the table.
Synonym is alias of table (and some other database objects).
View is a short hand for SQL select statement, which can present the table in a different format. From user's point of view, view and table will not have different, except that user cannot modify data in a view.

How to create new database?

2009-06-29T08:00:00.000+08:00

Steps to create new database:

Run Database Configuration Assistant (DBCA), either from Start Menu or by command prompt issue "dbca" command.

Select Create a Database option and click Next button.

Select General Purpose and continue.
Global Database Name and SID are simply refer to your database name. Key in your database name and continue.

Enterprise Manager is Oracle default management tools for database and it is in a separate installation. Untick Configure the Database with Enterprise Manager and continue.

Key in password for system user and continue.

Select File System in order to have the option to select where to create the database, then continue.

Select Use Common Location for All Database Files and key in the location where the database to be created, then continue.

Untick Specify Flash Recovery Area and continue.

Just continue.

Leave as default and continue.

Continue.

Finally click Finish button to create database.

What is relational database?

2009-06-28T12:00:00.001+08:00

Oracle RDBMS

Database is a place where you store your data, like text file, spreadsheet, and further more relational database.

What make relational database different from the others is that, it uses logical tables to store data, and users need to interact with relational database using SQL (Structured Query Language).

For example if you create a program that store data in a text file, you need to play around with the file format or structure, then direct read from and write into the text file. While if you're using relational database, you need to deal with tables and issue SQL statement to do anything.

Another difference between relational database with others is that, it needs a DBMS (Database Management System) in order to work. All the SQL statement you issued need to go through the middle man DBMS.

That's where server come into the picture. Normally people will install DBMS and database (aware that it is 2 different entities, since you can install DBMS without any database) into a server and let users to access through client tools, website or customized programs.