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Data Querying Methods in Relational Databases

This document explains various data querying examples using SQL-like syntax. It includes comparisons based on personal attributes such as age and weight for the Person entity, and filtering based on ratings and specific names for the Employee entity. The examples demonstrate how to apply selection criteria effectively to retrieve relevant data. Understanding these basics is essential for efficient data management and retrieval in structured databases, showcasing the importance of precise queries and their impact on data analysis.

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Data Querying Methods in Relational Databases

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  1. Example1 • σage>= 30 (Person) • σage>=weight (Person)

  2. Example2 • σrating > 8 (Employee) • σsname = “Jamal” (Employee)

  3. name, hobby (Person) .  Hobby (Person)

  4. Example4 R S R x S

  5. S R Example5 R X S

  6. Example

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