42597
Description
Chapter 5
- Database Terms
- Table
- About "things" and made up of records.
Rows, columns and a unique name
- About "things" and made up of records.
Rows, columns and a unique name
- Record
- Single row within a table, data about a
single event, fields and data types
- Single row within a table, data about a
single event, fields and data types
- Field
- Individual data item within a record, unique name
- Individual data item within a record, unique name
- Primary Key
- Field that allows a record to be uniquely identfied
- Field that allows a record to be uniquely identfied
- Foreign Key
- Links tables together, field in one table that is
linked to the primary key in another
- Links tables together, field in one table that is
linked to the primary key in another
- Entity
- Anything you can store data about,
singularly and written in capitals
- Anything you can store data about,
singularly and written in capitals
- Attribute
- Characteristic of an entity
- Characteristic of an entity
- Duplicate Data
- Exists in two tables,
removed by normalisation
- Exists in two tables,
removed by normalisation
- Referential Integrity
- makes sure it is impossible to
enter a reference in the database to
a link which does not exist
- makes sure it is impossible to
enter a reference in the database to
a link which does not exist
- Table
- Relationships
- One-to-One
- One record in one table, that can only
be linked to one record in another table
- One record in one table, that can only
be linked to one record in another table
- One-to-Many
- One record in one table
that can be linked to many
records in another table
- One record in one table
that can be linked to many
records in another table
- Many-to-Many
- Many records in one table that
can be linked to many records
in another table
- Many records in one table that
can be linked to many records
in another table
- One-to-One
- Parameter Queries
- Simple
- Only one parameter value
- Only one parameter value
- Complex
- More than one parameter value
- AND, OR, NOT, >, <
- More than one parameter value
- Dynamic
- Asks the user what to search for
- Asks the user what to search for
- Static
- Cannot be changed,
"hardcoded"
- Cannot be changed,
"hardcoded"
- Simple
- Normalisation
- 0NF
- When data is first collected and
put into the table
- When data is first collected and
put into the table
- 2NF
- 1NF, non-key fields
found using primary key
- 1NF, non-key fields
found using primary key
- 3NF
- 2NF, non-key
items dependent
on primary key
- 2NF, non-key
items dependent
on primary key
- 1NF
- Must have a primary key,
unique field names, no
repeated fields, data is atomic
- Must have a primary key,
unique field names, no
repeated fields, data is atomic
- Advantages/
Disadvantages
- increases integrity, data
consistency, removes
redundant and duplicate
data, easier maintenance
- Reduced database performance,
not appropriate for some data types
- increases integrity, data
consistency, removes
redundant and duplicate
data, easier maintenance
- 0NF
- Data Dictionary
- Table Security
- Who has access to the table
- Who has access to the table
- Keys
- Primary and foreign
- Primary and foreign
- Table Name
- Unique name for each table
- Unique name for each table
- Field Data Type
- Data type allocated to each field
- Data type allocated to each field
- Field Length
- Number of characters allocated to
field
- Number of characters allocated to
field
- Field Default Value
- Value that automatically appears
- Value that automatically appears
- Field Validation
- Any validation applied
- Any validation applied
- Indexes
- Any field indexed
- Any field indexed
- Field Name
- Each field is indentified
- Each field is indentified
- Relationships
- Between tables
- Between tables
- Table Security
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