1.3.2 Databases definitions/info

• data should be atomic • there should be a primary key

• must be in NF 1 • No partial key dependencies

a value that varies in line with another value

creating another table with the foreign keys which link the two other tables together

a link to the primary key in another table

• must be in 2NF • no non-key dependencies

any fields which are not designated a primary key or part of a primary key

each attribute is dependent on the key, the whole key, and nothing but the key

• searching and retrieving records • inserting new records into databases • deleting records and individual items of data from tables • updating existing data and replacing it with new data

• SQL statements are made up of key words • convention to write key words in caps • each SQL statement is terminated with a semicolon • convention to write longer statements over multiple lines

• delete a table • delete an entire database

allow you to retrieve data from databases

SELECT __Field/s__ FROM __Table__;

SELECT * FROM __Table__;

SELECT __Fields__ FROM __Table__ ORDER BY __selected field__;

SELECT __Fields__ FROM __Table__ ORDER BY __selected field__ DESC;

SELECT __Fields__ FROM __Table__ WHERE __condition__;

used with the WHERE keyword to return records in the table are in the same format as the given condition

a specification as to how multiple tables are joined together

SELECT __Fields__ FROM __Table__ JOIN __second table__ ON __field that they are connected with__;

INSERT INTO __table__ VALUES __values__;

DELETE FROM __table__ WHERE __criteria__;

a single logical unit of work

A - atomicity C - consistency I - isolation D - durability