DATABASE DEFINITION
Definition of the database are A set of data that stored in the magnetic disk, optical disk or other secondary storage Collection of integrated data-related data of an enterprise (company, government or private), the ERD is used for manufacturing production planning, actual production data, data ordering materials, etc.
DATABASE MANAGEMENT SYSTEM
Database Management System is Collection / database combined with software applications that are based database. This Application programs are used to access and maintain the databases. So with DBMS can provide an environment that is efficient and easy to use, withdrawal and storage of data and information. It can help user more easier to access the data
BIT, BYTE, FIELD
Talk about database, we also talk about bit, byte and field. Bit is the smallest pieces of data that contains the value 0 or 1. Byte is set of bit-bit similar. Field is set of byte-byte similar, in the database used the term attribute ATTRIBUT/FIELD Attribute/field is the nature or characteristics of an entity that provides provide detail on these entities. Some relationship in database can also have attributes Example attributes: STUDENTS: NIM, NAME, ADDRESS CAR: NOMOR_PLAT, COLOR, TYPE, CC TYPES ATTRIBUTE The types of attribute can divided into:
• Single vs. multi value This attribute can be filled only at most one value o Single can be filled with more than one value with the same type of o Multi value
• Atomic vs. composition This attribute can not be divided into the attributes of smaller o Atomic can not be divided into a smaller attribute o Composition is a combination of several attributes of a smaller
• Derived attribute The derived attributes resulting from the date of birth attribute value can be derived from the value of other attributes
• Null Value attribute The Attributes that have no value to a record
• Mandatory attribute Value Attributes must have values
RECORD/TUPLE
Record/tuple is a line of data in a relationship. This record Consists of the set of attributes where the attribute-attribute-attribute is to inform each other entity / relationship fully
ENTITY FILE
File is a collection of similar records and have the same elements, the same attributes but different data in its value. Some of the File Type In processing applications, files can be categorized as follows: Master File, Transaction File, File Report, File History, File Protection, Job File DOMAIN The Domain is the set of values that are allowed to reside in one or more attributes. Each attribute in a database relational is defined as a domain
ELEMENT KEY DATA
The element key of record which is used to find these records at the time of access, or can also be used to identify each entity / record / line.
SPECIES OF KEY
There are some Species of key that the database have, those are:
• Super key is one or more attributes of a table that can be used to identify entity / record of the table are unique (not all attributes can be super key)
• Candidate Key is a super key with minimal attributes. Candidate must not contain a key attribute of the table so that the other candidate key is certain super key but not necessarily vice versa.
• Primary Key One of the key attributes of the candidate can be selected / specified a primary key with the three following criteria: 1. Key is more natural to use as reference 2. Key is more simple 3. Key is guaranteed its uniqueness
• Alternate Key is an attribute of the candidate key is not selected to be primary key.
• Foreign Key is any attribute that point to the primary key in another table. Foreign key will be going on a relationship that has cardinalities one to many (one to many) or many to many (many to many). Foreign key is usually always put on the table that point to many.
• External Key is a lexical attribute (or set of lexical attributes) that values are always identify an object instance.
ERD (ENTITY RELATIONSHIP DIAGRAM)
ERD is a model of a network that uses word to order is stored in the abstract system. The Differences between the DFD and ERD are if DFD is a model of network functions that will be implemented by the system then ERD is a model that emphasizes the network data on the structure and relationship data
ELEMENTS OF THE ERD
The elements of the ERD can divided into:
• Entity In the ER Diagram Entity is described with the form of a rectangle. Entity is something that exists in the real system and the abstract where the data stored or where there are data.
• Relationship ER diagram on the relationship can be described with a lozenge. Relationship is a natural relationship that occurs between entities. In general, the name given to the verb base making it easier to do the reading that relation
• Relationship Degree is the number of entities participating in a relationship. Degree which is often used in the ERD.
• Attribute is the nature or characteristics of each entity and relationship
• Cardinality tupel indicates the maximum number that can be related with entities on the other entity
DEGREE OF RELATIONSHIP
There are some kinds the degree of relationship:
• Unary Relationship model is the relationship between the entity originating from the same entity set.
• Binary Relationship model is the relationship between 2 entities.
• Ternary Relationship is a relationship between the instance of 3 types of entities are unilateral.
CARDINALITY
There are 3 cardinality relations, namely
• One to One: Level one to one relationship with the one stated in the entity’s first event, only had one relationship with one incident in which the two entities and vice versa.
• One to Many or Many to One: Level one to many relationship is the same as the one to many depending on the direction from which the relationship to be seen. For an incident on the first entity can have any relationship with many incident on the second entity, if the one incident on the entity the second can only have one relationships with the incident on the first entity.
• Many to Many: if any incident occurs in an entity many have relationships with other entities in the incident.
Notation (E-R diagram) Symbolic notation in the ER diagram is 1. Rectangle represent the collective entity 2. Circle represent the attributes 3. Rhomb part explains collective relationships 4. Line as the set of relationships between the entity and the collective entity with that Set of attributes
