↕️ Hierarchical Data Model

Also known as HDM

Pros:

• Data can be retrieved easily due to the explicit links between the table structure
• Referential integrity is always maintained. i.e. any changes made in the parent table are automatically updated in a child table
• Promotes data sharing
• It is conceptually simple due to the parent-child relationship
• Database security is enforced
• Quick access at root nodes
• Efficient with 1:N relationships
• A clear chain of command or authority
• Increases specialisation
• Clean results
• High performance

Cons:

• If the parent table and child table are unrelated, the adding a new entry in the child take is difficult because additional entry must be added in the parent table
• Complex relationships are not supported
• Redundancy which results in inaccurate information
• Change in structure leads to change in all application programs
• M :N relationships are not supported
• No data manipulation or data definition language
• Lack of standards
• Poor flexibility
• Difficult to implement into a database
• Communication barriers
• Organisational disunity
• Rigid structure

What does the N mean?

N means many
Example:
M : N = Many to Many

Disunity

NOUN
1. disagreement and conflict within a group.