What is a Data Dictionary?
The data dictionary consists of two words, data, which represents data collected from several sources, and dictionary, which represents where this data is available. The data dictionary is an important part of the relational database because it provides additional information about the relationship between several tables in the database. A data dictionary in a DBMS helps users manage data in an orderly and orderly manner, thereby preventing data redundancy.
Below is a data dictionary that describes the table that contains employee details.
|
Field Name |
Data Type |
Field Size for Display |
Description |
Example |
|
EmployeeID |
Integer |
8 |
Unique ID of each employee |
100025 |
|
FullName |
Text |
30 |
Full name of the employee |
Emily Johnson |
|
DOB |
Date/Time |
10 |
Date of birth of employee |
1990-05-15 |
|
PhoneNumber |
Integer |
10 |
Phone number of employee |
555-123-4567 |
Some of the advantages of using a data dictionary are:
- In DBMS, the data model provides very little information about the database, so the data dictionary is very important to get the right knowledge about the entities, relationships, and attributes that exist in the data model.
- The data dictionary provides consistency by reducing data redundancy in data collection and use among different team members.
- Data dictionaries provide structured analysis and design tools by implementing data standards. Data standards are sets of rules that govern the collection, recording, and presentation of data.
- Using a data dictionary helps define the naming convention used in the model.
What is Data Dictionary?
In a database management system (DBMS), a data dictionary can be defined as a component that stores a collection of names, definitions, and attributes for data elements used in the database. The database stores metadata, that is, information about the database. These data elements are then used as part of a database, research project, or information system.
It stores all information about relationships or tables, from the schema and constraints used. All metadata is preserved. In general, metadata refers to information about data. Thus, storing the connection scheme and other metadata in a single structure called a data dictionary or system directory. A data dictionary is like an A-Z dictionary of a relational database system that stores all the information about every relationship in the database.