SQL and databases

fixed fields with data types has metadata

no discernible structure no metadata cannot be queried without being transformed

collection of information that is organised so it can be accessed, managed and updated

column, single piece of data about an entity

rows, the group of fields about a specific entity

field that identifies each record uniquely

field in one table that is the primary key in another table, links the tables together specified by a *

unstructured information/data makes it hard to work with large datasets and to interpret

data base with one table

has multiple tables that are connected through their key fields - foreign key

• flat file data bases can lead to redundant data (repeats) - inconsistencies likely to be introduced (as you have to manually add everything in so more likely to make mistakes)

structured query language

SELECT Field(s) FROM Table WHERE Condition ORDER BY Field ASC/DSC

SELECT Title FROM Albums

SELECT Title, Artist FROM Albums WHERE Year > 2015 ORDER BY Year DESC

SELECT Name, Stream_Count, Title FROM Albums, Songs WHERE Albums.ID = Songs.ID

SELECT Teachers.Name, Room FROM Teachers, Classes WHERE Classes.Name = “12B/It” AND Teachers.TeacherCode = Classes.TeacherCode

Adds a record to a table INSERT INTO Table (fields) VALUES (values)

gaps, empty field in record

removes record from table DELETE FROM Table WHERE Field = Value

changes value or values in table UPDATE table SET Field = Value WHERE condition

UPDATE Products SET Price = “£2.99” WHERE Name = “Protractor”