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Databases and SQL - Coggle Diagram
Databases and SQL
Table
a collection of data about one subject - e.g. students, customers, staff, products, orders - 1 large database can contain many tables
Data type
integer, float, boolean, character, string
Key field/ primary field
a field where the data is different for every record - used to uniquely identify a record e.g. ID Number
Database
A database is a collection of organised/structured data.
Database advantages
It allows vast quantities of related data to be stored together.
Complex searches, sorts and modifications can be performed on the data using SQL (structured Query Language)
Record
all the items of data for one person or thing - rows
Field
1 item of data - columns - e.g. ID number, surname, first name, date of birth, email address - each field uses a specific data type to store its data e.g. string, integer, float, date/time, Boolean
From
FROM TableName - specifies the name of the table that the fields are to be selected from
Boolean operators
(AND - both conditions must be true, OR - only one condition has to be true, NOT - the condition(s) must be false)
Comparison operators
( =, <> or !=, >, >=, <, <=)
SQL
SQL is a language used to create, search (query) and make changes to databases - especially web based. At GCSE Level, you need to know how to search databases by selecting the appropriate data to display. You do not need to know how to create or makes changes to databases using SQL.
Select
SELECT FieldName1, FieldName2 etc - only selects the specified fields
Where
WHERE Fieldname & Conditions - specifies the conditions that a field needs to meet in order to be selected
*
SELECT * - selects all the fields