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-# SQL 
\ No newline at end of file
+# SQL Database
+- Database is a collection of related data.
+- Data is: known facts that can be recorded and have implicit meaning.
+- Database is a collection of values in digital form, organized in a efficient way
+
+## Data modeling
+
+Data model is a collection of concepts to describe the structure of a database.
+
+Structure of a database includes data types, relationships and constraints that apply to the data.
+
+- High Level: Conceptual data models
+- Low Level: Physical data models
+- Representational: implementational data models
+