Databases – Data Dictionary and
Data Types
ICT@
WJEC Applied ICT
Data Dictionary
According to Wikipedia:
A data dictionary, as defined in the IBM Dictionary of Computing, is a "centralized
repository of information about data such as meaning, relationships to other data,
origin, usage, and format.
In other words, a 'data dictionary' describes the structure and attributes of data 'items'
to be used within a software application (usually a database).
A data dictionary includes the names and descriptions of the tables and the fields
contained in each table. It also documents information about the data type, field
length and other things such as validation.
The main purpose of the data dictionary is to provide metadata, or information about
data. Technically, it is a database about a database. There is no one set standard in
terms of layout or the level of detail to which a data dictionary should be written.
Software development teams need a comprehensive data dictionary to refer to during
the development and maintainance of a new database. This is so that they are all
working using the same data formats when reading or writing data.
Databases – Data Dictionary and
Data Types
ICT@
WJEC Applied ICT
Data Dictionary – What is in a data dictionary?
Databases – Data Dictionary and
Data Types
Data Dictionary – An Example
ICT@
WJEC Applied ICT
Databases – Data Dictionary and
Data Types
ICT@
WJEC Applied ICT
Data types
There are a number of data types that are available for use in creating
databases below are some.
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Text
Memo
Number
Date/Time
Currency
Autonumber
Yes / No (boolean)
OLE Object (Access)
Hyperlink
Attachment (Access)
Calculated (Access)
Lookup - from another table, data type could vary