Unit 7 P1

3) The SQL keyword PRIMARY KEY is used to designate the column(s) that are the primary key for the table.

Relational data is when you can put data in a computer one time and it grows

A row in a table is associated to one and only one row in another table. An example of a one-to-one relationship is a person can have one social security number and a social security number can only be assigned to one person.

which contains a foreign key for both a and b. By convention, this table is called

All of the examples above are ways a database can keep, retrieve, send and look for a precise data to another piece if the database system. Attributes have a big role in any database as makes the storage of information held stronger.

Entities are tables in databases, a database can have more than one entity, and entities are better described as a table that is populated with data and information.

The hierarchical typical structure has levels which shows one –to – many also relationship between a parent and children divisions. The main key this models which following by each parent can have many children as well each child has simply one parent.

2) An underlined attribute is the primary key and an italicized attribute is a foreign key.

The main feature of a relation database would be the primary key. It is a unique identifier set to each and every record which moves across different tables in relationships. A good example of a primary key is a Social Security number. The primary keys job is to make each record unique and lets data to be kept in more than one table. Each table within a relational database will have to have a field for the primary key.

Relation database is a database model in which information is stored in separate tables stored in a linked

When we design a database for a relational system, the main objective in the development of a logical data model is to create an accurate representation of the data its relationship and constraints. The data should be split in different tables, which can then be joined together based on their relations with each other and the data found in each one of them. These tables should therefore be designed well to save on space and ensure that cases on data inconsistency are eliminated. Another aspect, which will be saved on, is space that is occupied by repetitive data.

Relationships on a database establish a connection between two associated and logically related tables, that each have similar data. An example may be a table that contains names of certain students, and another table that contains the student's ID, the code of library books, and the dates on which each specific student checked out that particular library book. Without association of relationship on the relational database, the two tables would be independent figures with librarian lacking a method for associating student with his/ her item. The library, accordingly, would have to close down in a short period of time. The database connection, on the other hand, allows a connection to be drawn between the Student's table and the Student's instrument table (that represents the books that the student checks out).

The main feature of a relation database would be the primary key. It is a unique identifier set to each and every record that travels across different tables in relationships. An example of a primary key is a Social Security number. The primary keys job is to make each record unique and it lets data to be kept in more than one table. Each table within a relational database will have a field for the primary key.

A matrix composed of intersecting rows (entities) and columns (attributes) that represents an entity set in the relational model. Tables are also referred to as relations.

Database models represents the way data is stored and determines how data is retrieved and manipulated. There are four main database models. They are: Flat, Relational, Hierarchical and Network. (Johnson., 1997)