Databases - All Flashcards
Define Database
Store of Data - Lots of data which is being stored in a database.
Organised - Data which is organised into records. (e.g, A school database will have a record per student)
Persistent - Means that a Database is on a non-volatile secondary storage such as a hard disk.
What is a database often described as?
A database is described as “a persistent organised store of data”.
What does DBMS stand for? And what does it do?
Database Management System
The separation of the programs from the data is achieved using a database management system (DBMS). This is a software system that provides controlled access to the database. This separation is sometimes called program‐data independence.
What is a DBMS?
DBMS or (Data Base Managment System) is a software system that provides controlled access to the database. This separation is sometimes called program-data independence.
Name the key features of a database management system?
Provides separation between the applications and the database. Allow multiple applications to use a single database. Provides security in terms of views and access rights. Can provide automatic backups if required. Includes forms, queries, reports.
On this table which field will be the Primary Key?
Why?
ProductID.
Because it is unique to each entry in the database, and its at the start of the column.
Define Data Duplication / Data Redundancy
Where the same data is stored more than once, unnecessarily. This often leads to inconsistency.
Explain the term entity.
A real world object, about which data is stored in a database, corresponds to a table in the relational database.
What is the difference between a relational database and a flat-file database?
A flat-file database contains all the data in one large single table.
A relational database splits key information into it’s own table and links the information using keys.
What is a form in a database?
A form allows the entry of specific information into the database. Most web forms that you fill in will link to a database. They only allow certain information to be entered, and that information may be validated.
What is a primary key?
A primary key is the unique piece of information for that row of the table. It is something that cannot be repeated in the database.
Your USERID for the school system is your primary key in the school database.
What is a query?
A feature of a DBMS that allows the database to be interrogated. It selects records from the database based on specified criteria.
e.g. Display all students in Year 8 only.
What is a database report?
Data are just facts and figures with no context. They can be processed into reports to convey information. Information is processed data that has context and meaning. A DBMS can take data from tables or the results of queries and present them in reports.
It might be a report on the screen, or an output formatted a certain way to a Word document or Excel spreadsheet.
The user chooses the information and how it is displayed to best suit their needs.
Define a primary key in a database table.
What is the purpose of a foreign key in a relational database?
A field in one table that is the primary key in another table and is used to create a relationship between those two tables.
What is a database record?
Data stored about one instance of an entity ie: one particular person or object.
Explain what a validation check is when entering data in a database.
Validation is when the computer software checks that the data entered is reasonable or sensible and conforms to rules about the type of data allowed. There are several types of validation that are used when creating an application:
• Range check: a number or date is within a sensible / allowed range
• Type check: data is the right type such as an integer or a letter or text
• Length check: text entered is not too long or too short, for example: a password is greater
than 8 characters, a product description is no longer than 25 characters
• Existence check: checks that a product or customer exists in the data base, for example: if an order is being entered in a system it checks if that product actually exists in the database
• Presence check: checks that some data has been entered, that is has not been left blank
• Format check: checks that the format is appropriate such as a postcode or email address
Describe some sensible validation checks on a web form that asks for a users date of birth.
- That the date is in the past.
- That the date is not over 100 years ago.
- That the information entered is actually a date.
What logical operators can be used to filter results when performing a query on a database?
NOT, AND, OR.
