computing Flashcards
Describe an entity
An entity is an object about which a database will store information.
An entity can be a person, an object or something abstract.
Describe an attribute
An attribute is an item of information that relates to particular entity.
Describe and use a primary key
A primary key is a field which uniquely identifies a record in a database.
In database design, primary keys are underlined e.g. EmployeeID
Describe and use a foreign key
A foreign key is a primary key from one table which is used in a second table to link the tables together.
Describe attribute types
Attributes can have different data types:
Text
Number
Date
Boolean
Describe and use attribute size
The size of a Text attribute is the number of characters which will be stored. If the attribute size is too small, it may result in data being lost, The size of an attribute is a measure of how much space the field will take up when stored in main memory or backing storage. .
Describe and use presence check validation
A presence check ensures that data is entered in a field.
Use a presence check to ensure important information is entered e.g. Name, Postcode date of birth mobile and email
Describe and use restricted choice validation
Restricted choice limits data entry to a set of acceptable values.
Use a restricted choice check to limit data entry e.g. red, white, silver, black, blue and grey.
Describe and use field length validation
Field length validation limits the number of characters that can be stored in a field.
Describe and use range validation
Range check ensures that data falls between two values.
Create an entity-relationship diagram
An entity relationship diagram (ERD) is a graphical representation of entities in a database, and their relationship to each other.
Create a data dictionary
A data dictionary contains information about the tables and fields in a database.
The information (known as metadata) should include:
Design and implement a solution to a query
A query is a request for data from a database table or tables.
A query design should include
Describe and use SQL select operations
The SELECT statement selects data from a database. It can be followed by a list of individual field names, or the asterisk (*) symbol can be used to select all of the fields in the table.
The FROM command is used to specify which table(s) to select data from.
Describe and use SQL order by operations
The ORDER BY statement sorts the results of an SQL query in ascending or descending order.
Describe and use <, >, = in SQL operations
The less than (<), greater than (>) and equals (=) operators can be used with the WHERE clause to refine SQL queries.
Describe and use AND, OR in SQL operations
The OR and AND operators can be used with the WHERE clause to refine SQL queries.
