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In computing, Database can be defined as collection of data information which interrelated. Relationships between data can be found in field/column keys from each data which is stored in the computer in a systematic way. Computer software that controls creation, maintenance, and the use of database is known as Database Management System (DBMS). The main objective of DBMS is to remove the responsibility of the client application to manage access, manipulation and organization data. The Database Management system provides an interface so a client can change, add, or query data. In relational databases, the interface consists of DBMS's driver or APIs, which accomplish the commands in SQL language. DBMS consists of executing and maintaining database, operate as interface between application programs and data files and separates logical and physical view of design data information. There are 3 basic components of DBMS:
The Data information Definition Language (structure of the database and defines the data elements, specific content)
The Data information Manipulation Language (can add and change the database)
The Data information Dictionary (Keep the definition of data information elements and characteristics of the each data- describe the data file, whom the access, etc [information issue])
The first appearance of table is in 1970s at IBM's relational algebra is a mathematical theory in relation to theory of sets. The purpose of this theory is to clarify and facilitate the use of database. In database, a single table is a set of data which is organized as table where columns are fields and rows are records (two-dimensional). It also has tuples and attributes. Each row can be defined by the appearing of values in a particular column that called as a candidate key. Each field has a unique name and it is corresponding data. This use to handle multiple fields in the table, every field must have a different name of each. Every table is physical implementation of a relationship between the various fields. A line of the table defines each match and the values of the field are in the same column. In addition, in designing a relational database, it is important to define all the tables and the different of their relationship.
In the following picture is an example of one of the table in database library and it has six columns and eighteen rows. Every tables in library are be built by columns and rows. All the tables in library database show all the library information. One table has relationships with other tables and each table has different name. Each field of these tables have a unique name.
Attributes can be described as a component of database which can identify the entities which differentiate these entities with other entities. Each attribute must be sufficient which can state the identity of an object, in other words, all attributes of each entity can recognize the uniqueness of an individual .The schema of data is linked one or more attributes with every other entity. Attributes also are known as field or column which should not include one kind of information for one row or tuple and also another kind of information for another tuple. There is a name in every column and it shows it own information. In database, there are two types of value key, primary key and foreign key. A value key can be contained by an attribute or a column. In addition, an attribute or a column which not contain of any value key only can represent one type data in a table.
In the picture below will show an example of attribute in a table. Below table is one of the tables in library database, book table. In the table, the mark in the author column is one of an attribute of these columns. The table contains 5 attribuites. The bookid in the table is a primary key and the categoryid is a foreign key. All columns in the following table have a different name in it and they also represent their own data.
Attribute in the author column in one of the library tables:
An attribute or column
A tuple (known as n-tuple) in mathematic is an ordered sequence of objects that describes the mathematical objects which have a structure. 0-tuple means a blank sequence. A tuple is distinct inductivity by the structure of an ordered pair. Mostly Tuples are printed with listing the elements within parentheses '()'. While In relational database, a tuple is a group of one or more attributes that represent all information which is essential for a particular object and it also known as a single row. Each row can be acknowledged by a primary key and a duplicate row is not allowed. Every tuple component can be recognized by a distinct name, known as attribute.
The picture below is an example of tuple in one of library table with the mark in it. In this table, it has 12 rows or tuple. In table below, there are no duplicate rows in it and in an unordered set.
Tuple or rowTuple can be seen in the mark in the table:
The primary can be described as a combination of fields or a group of fields that uniquely identify each row of a table. A primary key can consists of a single attribute or a set of attributes and it uniquely indentify all possible rows in the table. All databases provide mechanisms that support numbering used for primary key in the table with a list of people. A primary key is a case of unique key and the main different between primary key and unique key is that in a unique key is manually imposed implicit NOT NULL constraint, while in a primary key is automatically imposed implicit NOT NULL constraint. A single column that part of the primary key cannot consist a NULL value and every table in database only able to contain one primary key. In addition, a duplicate value is not permitted in the primary key, in the other word; it cannot contain a copy value in the primary key. The values in a primary key are could not be modified.
One of the examples is shown in below picture, memberid in is the primary of the library database or tables. The primary key (member id) contains numbers in the field. The table below only contain one primary key, there is no duplicate value in it, and there is no a single null value that contained by the primary key (null value cannot be allowed). The primary key in the following table is allowed the table to connect with other table with the help of foreign key in the other table.
No duplicate, no null, and the table contain one primary key.Primary key is in the right of the table with a mark.
COMPOSITE PRIMARY KEY
Composite primary key also called compound key or concatenated which has one or more fields. The composite primary key can be composed of several fields.
For the example, the entity has memberid and bookid operate as it is primary key, each column that build up the primary key are the simple key (every attribute represents unique reference when recognizing a book in one instance and category book) . On the other hand, in the same example, if we identified the book by book name, author, and date publication. In the table have bookid + author + date publication. Author and date publication are not simple key, it is a combination of column to identify the book. for that reason, the primary key for this entity is composite key. Compound key can be a foreign key and a foreign key can be a compound key.
The following picture is an example of compound key or composite key.
Memberid and bookid in the table.
Compound key or primary key
bookidBookid , author, datepblucation.
In context of relational database, the foreign key (or FK) is a limitation of reference between two tables. A foreign key identifies an attribute or set of attributes in a table as column or referencing a set of columns in another table (the referenced table). The column of the referenced table must be consisted of primary key or a unique constraint. Values in row of referendum column should be only in one row in the referencing table. Therefore, a record in the referenced table could not be included a set of values which does not exist in the referencing table. A table can has one or more foreign key and every may have different referencing tables. Every foreign key is imposed freely by the database system. Relationship between tables could be made by using foreign key and primary key (it is one of the fundamental principles of the relational database). A foreign key value must be same with the primary key or unique key value in order to make a relationship between the tables. Foreign key also can be primary key in another table.
Picture in the below is one of the examples of foreign key. The foreign key is on the right side with the mark in the table. The foreign key (categoryid) in the book table is the primary key of category table (categoryid) and there is a relationship between these two tables.
categoryidForeign key is with the mark in the right side (book table).
The foreign key is as primary key in category table and the relation between book table and category table are built.
Database crate by access (library database)
All information about member in library
J1: Member ID, is one of these attributes in the member table that shows the ID of people who become member. Each member has a different id.
J2: First Name, the first name of the people who has become a member.
J3: Last Name, the last name of the people who has become a member.
J4: Gender, the gender of the people who has become a member.
J5: Age, the age of the people who has become member.
J6: NIRC, the NICRC of the people who has become member. Each is different.
J7: Date joined, the date of people when they have become a member.
J8: address, the address of the people who has joined the member of library.
Primary keyDesign view of the member table.
Field name or column name
Data type of the field
All information about books in the library
J1: Book id, it shows the book's id in the library.
J2: Book name, name of the book which library has.
J3: Author, name of the person who writes the book.
J4: Date publication, date of the book came out.
J5: category id, id of the book's categories.
Design view of the book table.
Data field type
J1: Category id, is an book's category id.
J2: Category name, the category name of the book in the library.
Design view of category table.
Data type in the field
Information about the load book
J1: Member id, it shows the member who borrow book and return book.
J2: Date borrowed, it shows the date of members borrowed the book.
J3: Date returned, it shows the date of member returned the book.
J4: Book ID, it shows the book id which member borrowed and returned.
Design view of loan table.
Data type of the field
Foreign key key
No of books borrowed table
Information about number of the book borrowed and stocked
J1: Book id, id of the book that had been being borrowed.
J2: Books total, total of the books that stock in the library (every book is different)
J3: No of borrowed, the amount of the book being borrowed.
J4: Book remaining, the number of book that still can be borrowed by membership people or book that still stock in library.
Design view of no of books borrowed.
Data type of the fields
J2RELATIONSHIP BETWEEN THE TABLES
J1 : is one-to-many relationship, the primary (categoryid) key in the category table contain one row which relates to none, one, or more records in the table that have a relationship (categoryid).
J2: is one-to-many relationship, the primary (bookid) key in the category table contain one row which relates to none, one, or more records in the table that have a relationship (bookid).
J3: is one to-one relationship, two tables (books table and no of book borrowed table) can only contain one record on either table of the relationship. Primary key value in the both tables relates to only one record in the table that has a relationship.
J4: is one to-one relationship, two tables (member table and loan table) can only contain one record on either table of the relationship. Primary key value in the both tables relates to only one record in the table that has a relationship.