DBMS

SQL Queries & Operations

Hard
EST. TIME: 60 min

SQL Queries & Operations

To demonstrate advanced SQL operations including Joins, Subqueries, Triggers, Views, and PL/SQL blocks.

Theory & Concepts

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1. Introduction

Beyond simple storage and retrieval, SQL provides powerful tools for combining data from multiple sources and automating database logic.

2. Joins (Combining Data)

Joins allow you to retrieve data from two or more tables based on a logical relationship between them.

  • INNER JOIN: Returns records that have matching values in both tables.
  • LEFT (OUTER) JOIN: Returns all records from the left table, and the matched records from the right table.
  • RIGHT (OUTER) JOIN: Returns all records from the right table, and the matched records from the left table.
  • FULL JOIN: Returns all records when there is a match in either left or right table.

3. Advanced Objects

Views

Virtual tables based on the result-set of an SQL statement. Used to simplify complex queries or restrict access to sensitive data.

Triggers

Special stored procedures that are automatically executed (fired) when an event (INSERT, UPDATE, DELETE) occurs in the database.

4. Summary

Joins are essential for specific reporting needs in relational databases where data is normalized (spread across tables). Triggers ensure data integrity by enforcing rules automatically at the database level.

Procedure

1

Execute Joins

Select 'Employee' and 'Department' tables and run an Inner Join to see employees with their department names.

2

Define Trigger

Set up an 'Audit Trigger' that logs any salary update to a separate history table.

Learning Resources

Animated Lecture

SQL Joins Explained

Reference Notes

Advanced SQL Concepts

Self Quiz

SQL Joins Quiz

Ready to Start?

Launch the virtual simulator to perform database operations and see SQL queries in action.

Lab Status

Active Simulation

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