1.3.2 DATABASES

TO ensure data integrity, guarantees transactions are processed reliably.

ATOMICITY CONSISTENCY ISOLATION DURABILITY

A transaction must be processed in its entirety or not at all,

A transaction must not violate any of the defined validation rules(including referential integrity)

Simultaneous executions of transactions should lead to the same result as if they were executed one after the other,

Once a transaction has been committed it will remain so regardless of the circumstances surrounding it, such as in the event of a power cut.

It means that no foreign key in one table can reference a non-existent record in another related table

1) All field names must be unique
2)Values in fields should be of same type.
3)Values in fields should be atomic.
4)No two records can be identical
5)Each table needs a primary key.

1)Data is already in 1NF
2) Any partial dependencies have been removed(remove any many to many relationships formed)

Its when a field only partially depends on the primary key.

1) Create a linking table
2) Assign the primary keys from the two tables to the linking table as composite key.
3) Flip the many to many arrows to become two separate one to many arrows.

1) Data is already in 2NF
2) Remove any transitive dependencies

It is when the value of a field can be determined by another field which is not the primary key

Duplicate data in another hardware that mirrors every transaction and takes over as backup

Prevents simultaneous access to records in databases to prevent updates being lost or inconsistences occurring.

It is a declarative language used for fast CRUD in databases.

WHERE name LIKE "A%"

INSERT INTO <table name> (<field1>,<field2>)
VALUES(<value1>,<value2>)

DELETE FROM <table name>
WHERE <field name> = <condition>

JOIN <table name1>
ON <tablename2>.<field2> = <table name1>.<field1>

DROP TABLE <table name>

-manual
-OCR(character)
-OMR(mark)
- barcode readers

XML and JSON

manual methods like memory sticks
EDI used for automatic exchange of data between computers.

database management system used to make transactions reliable and for data integrity