9.

• Databases


  Structured persistent collections of data that allow us to arrange and store data into a series of tables for further querying and manipulation
• Types of databases


  • Single table or flat file databases
  • Relational databases
• Flat file database


  • Consists of one or more tables, each table consists of many separate records or rows, and each record is identical in its structure though its contents will vary, each record consists of a number of separate Fields or columns
• Relational database


  • Consists of multiple related tables, changing the lecturer code for a course will update the associated field for all students on that course
• Linking separate database tables to create a relational database is beyond the scope of the IGCSE course
• Field type


  Defined data types in a database, similar to data types in programming languages, can choose from text, alphanumeric, characters, booleans, integers, reals, or date time
• Primary key


  At least one field in each record that is guaranteed to be unique
• Primary key


  • Car registration number
  • Student ID
• Validation rules


  Can be assigned to any field of a table, including length checks, format checks, range checks, presence checks, and customizable rules
• Validation methods were discussed in detail in a previous video
• SQL


  Structured Query Language, a programming language for manipulating data in a database
• SQL statements


  • Support a wide variety of commands for manipulating a database
• Select statement


  1. Select fields

  2. From table

  3. Where criteria

  4. Order by
• The select statement is the one you need to be familiar with for the IGCSE
• SQL commands


  • Select population from world where name equals Albania
  • Select name, continent, area, population, GDP, capital from world where name equals Algeria
  • Select * from world where name like 'A%' and population > 1000000 order by name
  • Select count(*) from world where continent equals Asia
  • Select sum(population) from world where continent equals Europe
• Most of the code in the Python program is beyond the IGCSE syllabus
• The part of the program you do need to know about is where the SQL command is issued to the database