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Database - Coggle Diagram
Database
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Objectives
Data Models
Hierarchical data model: In this model, data is organized into a hierarchical structure similar to a tree.
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Their main objective is to provide an efficient and structured means for the storage, management and retrieval of large amounts of data.
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Data organization: A database system allows data to be organized in a structured way, using a data model that defines the way data is stored, manipulated, and related to each other.
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Relational model
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structure
Attributes: Attributes, also known as columns, represent specific characteristics or properties of the data stored in a table.
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Records: Records, also known as rows, are individual instances of data stored in a table.
Primary keys: The primary key is an attribute or set of attributes that uniquely identifies each record in a table.
SQL
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Operations on Assemblies
Union: The UNION operation is used to combine the results of two or more queries into a single result set.
Intersect: The INTERSECT operation is used to obtain the common records between two or more result sets.
Except – The EXCEPT operation is used to get records that are present in one result set but not in another.
These operations on sets are useful when you need to combine or compare datasets in a SQL query. They allow you to perform operations efficiently and express relationships between result sets in more complex queries.