Unit 1 (Online World) - Databases Flashcards
Table
It is a grid made up of rows and columns. Where these rows and columns cross-section we get a cell which we can enter data into.
Record
A row in a table. A record holds all the data on a single item. For example, if we have a table to store book details for a shop then each record is an individual book the shop sells and it will store all the data on that individual book such as the ISBN, book title and price.
Fields
An individual piece of data in a record. In the previous example we said that each record for a book will store the ISBN, book title and price. Well these three things are all examples of fields. Fields appear as columns in a database table.
Primary Key
Primary keys are fields that are always unique. For example a staff id number.
Foreign Key
A field in a database table that references a primary key field in another table.
Relationship (Databases)
Relationships are a link between two tables in a database created by copying a primary key field from table into another.
DBMS
A database management system is the software we use in order to create and manage a database and the data it stores. The DBMS (as we often refer to it as) acts as an interface between the user and the underlying data.
Some of its major functions are to allow us to define & modify the database structure, manage access to the data, allow us to search & sort the data and to allow us to insert and update the data.
SQL
Structured Query Language, also known as SQL, is a programming language that is used for database management and manipulation. All major DBMSs come with SQL implemented so you can use it for performing the common functions you might wish to complete on a database.
DDL
Data Definition Language – known as DDL for short, it allows us to define our database structure, such as the tables, fields & primary keys.
DML
Data Manipulation Language – known as DML for short, it allows us to manage our data, such as to insert, update & delete data or search for some specific data.
