What Is a Data Base?
A database is an organized collection of data,
generally stored and accessed electronically from a computer system.
Database design is the
organization of data according to a database model. The designer determines
what data must be stored and how the data elements interrelate. With this
information, they can begin to fit the data to the database model.
.What is a database?
At its simplest expression, a database is a gathering of information, here called data, stored on a server. The data is organized in a way it can easily be retrieved, managed and edited in significant ways by the end-user. The data could be something very simple such as personal information about clients or customers. It could also be inventory, sales, calls or anything anyone needs to track. It’s up to the user to determine what data needs to be aggregated and the format it will take.
When you’re using a database, the data is not stored on your computer’s hard drive but in the cloud on a server, somewhere. Using a database management system (DBMS), calls/queries are made to retrieve the information. This part is called the back-end. To present the data in a consequential way to the user, web developers create a web site and easy to use database applications. This part is called the front-end.
Even if there are many other database models such as hierarchical and network models, the relational database model is the most common. The relational database model was developed in the early 1970’s and it is still the most common model to this day. The data is stored in relations, taking the form of tables made of columns (fields) and rows (records/items). To access and interact with the data contained in a relational database, its user needs to use a relational database management system (RDBMS). The most common language used to query and manage relational databases is SQL (Structured Query Language).
SQL: The Classic
SQL is the language most IT experts use to interact with relational databases. These interactions are called transactions. To be efficient and accurate, transactions must be ACID (atomic, consistency, isolation, durability). Atomic means the transaction is all or nothing. Consistency refers to the fact that the database must remain in a consistent state before and after the transaction. Isolation means all transactions must be independent of one another. Durability refers to the fact that a transaction cannot be undone after the user has been notified of a successful transaction.
The best example I can find to explain SQL and its ACID properties is a banking system. Let’s say I want to transfer funds from my own account to my husband’s. There will be a series of calls or queries made to send the money from one account to the other. All calls must be answered and completed in order for the transaction to be completed. If a call fails, the transaction will not be completed and we’ll both keep our money (atomic). The information in each of our account won’t be affected by the transaction (consistency). Each call made to the database will only be related to our transaction (isolation). Finally, once the transaction is successful, we won’t be able to cancel it (durability).
The best-known RDBMS using SQL to create and query databases are IBM DB2, Oracle, Microsoft Access and MySQL. Examples of SQL-based databases citizens use every day include banking systems, computerized medical records, and online shopping to name just a few.
Pros of SQL
Well-known language, has been around for over 40 years.
Great storage solution (servers, not your hard drive!)
Allows query of the entire database
Allows relations between tables
The best solution for structured data and transactional needs
Can be accessed by many users at the same time
Cons of SQL
Need for deep expertise of programming skills: steep learning curve
Poorly designed database calls for poorly managed data
Some will say that SQL is not easily scaled-out
Not the best solution when dealing with data growing exponentially (ex. social media)
different between conventional and data base file
Conventional file
Conventional
file systems are capable of compressing files, while still permitting
applications to access data. The operating system automatically decompresses
the file when needed and compresses it again when the file is closed or saved.
While.
Data base file
Data base files store
data information, usually stored in a series of tables, table fields, and field
data values. The information is then stored and organized according to the data
model, the most common model structure being the relational model.
Similarities between conventional and data base file
Both conventional and database file stores
information’s and data
They are not a physical place one can go
store data, organize files.
Conventional and data base file are capable
of collecting files, data’s.
Data
Integration
Data integration is the
combination of technical and business processes used to combine data from
disparate sources into meaningful and valuable information. A complete data
integration solution delivers trusted data from various sources.
Data Integrity
Data integrity is the
maintenance of, and the assurance of the accuracy and consistency of, data over
its entire life-cycle, and is a critical aspect to the design, implementation
and usage of any system which stores, processes, or retrieves data.
Data Independence
The ability to modify
schema definition in one level without affecting schema definition in the next
higher level is called data independence
In relation to database describe:
Records key
Records are composed of
fields, each of which contains one item of information. A set of records
constitutes a file. For example, a personnel file might contain records that
have three fields: a name field, an address field, and a phone number field. In
relational database management systems, records are called tuples.
Primary key in database
A primary key is a
special relational database table column (or combination of columns) designated
to uniquely identify all table records. A primary key's main features are: It
must contain a unique value for each row of data. It cannot contain null values.
Secondary key in
database
A secondary key is a
non-identifying column or set of columns that can be used to find row in a
table. It is non-identifying in the sense that multiple rows may satisfy a give
secondary key value. Foreign keys are secondary keys as are any common filter
and join columns especially if they are indexed.
Data Base Occurrence
An additional data object
is the entity occurrence. For example, if customer is an entity, a customer
table represents the idea of customer; in it, each row represents one specific
customer, such as Sue Smith. Keep in mind that entities become tables,
attributes become columns, and entity occurrences become rows.
Data
Base Data Item
A data item is a
container of data that is registered with the server. The set of data items
registered with the server comprises the server's data store.
Data aggregation scheme.
Data aggregation is the
compiling of information from databases with intent to prepare combined
data sets for data processing.
database schema
A database schema is the
skeleton structure that represents the logical view of the entire database. It
defines how the data is organized and how the relations among them are
associated. It formulates all the constraints that are to be applied on the
data.