Database 101
Seri-2 #Overview
Database is a collection of data that is well managed according to interconnected provisions so that it is easy to manage. Through this management, the user can achieve success in finding information, storing information, and dumping information. Another basis of a database is a system that functions as a collection of files, tables, or archives that are connected and stored in various electronic media.
Database system is a computerized recording system; In other words, it is a computerized system whose overall purpose is to store information and to enable users to retrieve and update that information on demand. “C. J. Dates — Introduction to Database Systems
“The database system is a collection of application programs compiled with a database together with the DBMS and the database itself. Connoly and Begg, 2005.
Consists of 4 main components:
- User
- Hardware
- Software
- Data
Advantages of Database Systems :
1. Compatibility: no need for a massive paper file.
2. Speed: machines can retrieve and update data much faster than humans can.
3. Not too boring: a lot of boredom in hand-drawn documents has been eliminated.
4. Currency: accurate and current information is available on-demand at any time.
Advantages of the Database :
-The data can play.
-Redundancy can be reduced.
-Inconsistency can be avoided (to some extent).
-Window support can be provided.
-Integrity can be maintained.
-Security can be enforced.
-Conflicting requirements may deviate.
-Standards can be enforced.
Data Hierarchy
Bit, is a binary number system which consists of only two kinds of values, namely 0 and 1. The binary number system is the basic basis that can be used for communication between humans and machines (computers) which are a set of electronic components and can only distinguish between two conditions. (on and off). So the bit is the exact unit of form of data.
Byte, is the exact part that can be addressed in memory. A byte is a conventional set of bits consisting of a combination of eight bits. One byte is used to encode one character in memory.
A field, is a unit called data. A field is a set of bytes that have meaning. Example: Joni which is the name field. So a field is like a collection of characters that make up a word.
Record is a collection of items that are logically related to each other. Each record can be recognized by something that recognizes it, which is a key field. Figure 1 is an example of a record. So a record is like a collection of words that form a meaningful sentence, for example, picture 1 represents a sentence: Joni completed the MIS course (code IS101) with an A.
File, or table, is a collection of related and logically related records. File creation and maintenance are very important factors in management information systems using computers. So a table is like a collection of rows/records that form a meaningful table, for example, Figure 2 represents a table of values for DB courses.
The difference between databases and static data is that static data refers to a fixed set of data — or, data that remains the same after it has been collected. Meanwhile, the database is a collection of information that is stored systematically and can use a computer program to obtain it from the database.
Database Management System (DBMS) is a software system that supports users to define, create, upgrade, and control access to databases. Connoly and Begg, 2005
Example:
- Microsoft SQL Server Access Microsoft
- Fortune teller
- PostgreSQL
- MySQL
- NoSQL
- MongoDB, etc.
DBMS
The definition of a DBMS is a system or software specifically designed for the organization of a database and runs operations on data that is managed by many users. The main purpose of using a DBMS in computer networks is to avoid chaos in the processing of large instruction data. The DBMS is an intermediary between the user and the database, and to be reliable with a DBMS, the user must use the specified database language.
Data warehouse
According to Ralph Kimbal, a data warehouse is a system that extracts, performs, adapts, and sends data sources to a dimensional data storage and further provides support for query implementation and analysis in the framework of decision making.
Big Data
Big Data is a technology built on three dimensions, namely Volume, Velocity, and Variety of data counterparts. Volume here refers to the big data it holds. Speed refers to the speed of data. Variety refers to the many types of data that are managed. Big Data appears based on the resulting large and various types of basic data. Variety refers to the many types of data that are managed. Big Data appears based on the resulting large and various types of basic data.
Entity-Relationship Model
Describes things that are interrelated in a particular knowledge domain. The basis consists of the type of entity (which classifies things of interest) and determines the relationships that can exist between entities (examples of that type of entity) are usually formed to represent things that are business needs. to be an abstract data model, which defines data or information structures that can be implemented in a database, usually a relational database.
In general, Entity-Relationship is built for 2 or 3 levels of abstraction :
1.Conceptual Data Model, the highest-level ER model that contains the least detailed details. It does however specify the overall scope of what will be included in the model set. Conceptual ER models typically define master reference data entities that are commonly used by organizations.
2. Logical Data Model, the logical ER model does not require an ER conceptual model, especially if the scope of the Logical ER model only includes the development of different information systems. The ER Logical Model contains more details than the ER conceptual model.
3. Physical Data Model, one or more physical ER Models can be developed from each logical ER model. The physical ER model is usually developed for use as a database. Thus, each physical ER model must contain sufficient detail to generate a database and each physical ER model is technology dependent as each database management system is somewhat different. Examples of using the physical ER Model include database tables ,. database indexes such as unique key indexes, database constraints such as a foreign key constraint or commonality constraint, ER Models are also commonly used to design modifications to relational database objects and to maintain the structural metadata of the database.
Modeling Entity-Relationship :
Entities are something that is important to users that need to be represented in database files. An entity represents a single theme or topic. Entities are limited to things that can be represented by one table.
A relation is a two-dimensional table that has certain characteristics. Dimensional tables, like matrices, consist of rows and columns. Relationship Characteristics:
-Rows containing data about an entity
-Column contains data about the attributes of the entity
-The table cell contains one value
-All entries in the column are of the same type
-Each column has a unique name
-Column order is not important
-The order of the rows is not important
-No two lines are identical
A key is one (or more) columns of a relation used to identify rows.
1. Composite Key, is a key that contains two or more attributes. For example of Composite Key to identify family members, you need to know the clan (eg Pasaribu, Siagian, etc.). The composite key is (Marga)
2. Candidate Key, the Candidate key is called “candidate” because it is a candidate to be a unique primary key. An attribute, or super key that uniquely identifies a specific occurrence of an entity.
3. Primary Key, is the candidate key that is selected as the primary key for the relationship. If you know the primary key value, you will be able to uniquely identify a single row key. A rule where the function is to differentiate between rows and rows in the table and is unique. Primary Key Example: Employee file contains attributes: parent number, ID card number, name, place of birth, date of birth, address, city. The master number and ID card number are the candidate key (Candidate Key) and the primary key is the one selected from the candidate key. For example No. the parent is made the primary key, then the primary key is the parent number.
4. Foreign Key, is the primary key from one table that is placed into another table. To maintain a relationship, it is necessary to create a foreign key. An attribute to complete the relationship that indicates to its parent, it means that the field in the table is the guest key from another table. Example of Foreign Key: There are 2 tables, the first table is mhs and the second table is matkul, in the mhs table there is nim, name, address, id_matkul, and in the matkul table there are id_matkul, nm_matkul, sks. nim in the mhs table is the primary key. Meanwhile, the primary key in the matkul table is id_matkul. Then id_matkul attaches to the mhs table which we call the foreign key. Usually called a table containing foreign keys as a child table because the table links to other tables. Meanwhile, the related table I call the parent table. In the example table above, mhs is the child table while matkul is the parent table.
5. Surrogate Key, is a unique numeric value that is added to the relation to the server as Primary Key. These Key Values have no meaning to the user and are usually hidden forms, questions, and reports. This key is often used instead of a composite master key.
The various degrees of relation/cardinality includes:
1. One To One, which means that each entity in the entity set A is associated with the most one entity, and vice versa, each entity in the entity set B is associated with the most one entity in the entity set A.
2. One To Many, which means that each entity in the entity set A can relate to many entities in the entity set B, but not vice versa, where each entity in the entity set B relates to the most one entity A.
3. Many To One, which means that each entity in the entity set A can relate to at most one entity in the entity set B, but not vice versa, where each entity in the entity set B can relate to many entities A.
4. Many To Many, which means that each entity in the entity set A can relate to many entities in the entity set B, and vice versa, where each entity in the entity set B can relate to many entities in the entity set A.
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