International IT University IS 107 Lab work 6

Data storage and manipulation
Goal of the laboratory work is the development of a database: creating tables for storing
information, keys and links between tables, creating and executing queries
In today's information age, there is a need to effectively organize information for later search.
Data can be stored in both structured and unstructured forms. When data are stored in a structured
form, they are converted into information that can be used by all to process and analyze the data.
Microsoft Access is one of the most common database management systems (DBMS), which is
considered a relational database management system.
MS Access is part of the MS Office group and represents a set of data and objects. MS Access
objects: table, query, form, report, macro, module. For assimilation of creation of a database and data
manipulation in it we will be limited to consideration of the basic objects, such as the table and inquiry.
The table consists of a combination of rows called records and columns - fields (see Figure
6.1). The column of the table corresponds to some attribute. An attribute is a characteristic of an object
that has its own name and type.
Figure 6.1 - The table with records and columns – fields
In the table, all instances of the object must be unique. For example, in life it happens that the
names of movies are the same, but in the database, they must represent each individual object.
Therefore, an identification number is used which is not repeated, i.e. each object must have a key
called primary. The primary key is not an empty field or a set of fields that define the uniqueness of the
record.
A potential key is a generalization of the notion of a primary key. Just like a primary key,
potential keys have the property of unique identification of a record with respect to it, but if only one
primary key has to be selected with respect to it, there can be several potential keys (the primary key is
selected from the potential keys).
The external key is a set of object attributes; each value of the external key corresponds to the
value of the potential key. External keys are used to bind records in relational databases.