1. Relational/Structured (Data has schema/fixed type of data)
   1. Relational DB is stored as row (i.e. one identity)
   2. Columnar is stored as columns
2. Unstructured (media/blob)
3. Non-relational/Semi-Structured (json, yaml, xml, etc.)
4. Graph
   1. Has nodes
   2. Relationships between different types of nodes (entities)

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