SQL-TRAINING-IN-HYDERABAD

SQL-TRAINING-IN-HYDERABAD

SQL-TRAINING-IN-HYDERABAD

Blog Article

1. Introduction to SQL

SQL (Structured Query Language) is a special language used to manage and interact with databases. A database is a collection of information stored in a structured way. SQL helps us store, retrieve, update, and delete data easily.

Example: Think of a database as a giant digital notebook where companies store employee records, customer details, or product information. SQL helps us find and organize this data quickly.

2. SQL Installation & Setup

Before using SQL, we need to install software like ( Snowflake)

  • MySQL (Popular for websites)

  • SQL Server (Used by large companies)

  • PostgreSQL (Great for handling complex data)

Once installed, we use SQL clients like MySQL Workbench or SQL Server Management Studio (SSMS) to write SQL commands easily.

3. SQL Basics

  • Data types: These define what type of data we can store (e.g., numbers, text, or dates).

  • Creating databases & tables: We need a structure to store data, just like an Excel sheet has rows and columns.

  • CRUD Operations

    • Create – Add new data

    • Read – View existing data

    • Update – Modify existing data

    • Delete – Remove unwanted data

Example: Storing student information in a table.

CREATE TABLE Students ( ID INT PRIMARY KEY, Name VARCHAR(50), Age INT, Grade VARCHAR(5) );

4. Querying Data (SELECT Statements)

  • SELECT: Used to retrieve information from a table.

  • WHERE: Used to filter results (e.g., show only students older than 18).

  • ORDER BY: Used to sort results (e.g., arrange students by name).

  • DISTINCT: Removes duplicate values.

Example: Get a list of all students older than 18.

SELECT * FROM Students WHERE Age > 18;

5. SQL Functions

Functions help us perform calculations or modify data.

  • Aggregate Functions (SUM, COUNT, AVG, MAX, MIN) – Used for calculations on multiple rows.
    Example: Find the average age of students.

    SELECT AVG(Age) FROM Students;

  • String Functions (CONCAT, LENGTH, LOWER, UPPER) – Used to modify text.
    Example: Combine first and last names.

    SELECT CONCAT(FirstName, ' ', LastName) FROM Employees;

  • Date Functions (NOW, DATE_FORMAT) – Used to work with dates.
    Example: Get today’s date.

    SELECT NOW();

6. Joins & Relationships

When data is stored in multiple tables, joins help combine them.

  • INNER JOIN – Shows only matching data from both tables.

  • LEFT JOIN – Shows all data from the first table and matching data from the second.

  • RIGHT JOIN – Opposite of LEFT JOIN.

  • FULL JOIN – Shows all data from both tables.

Example: Get students along with their class names from a "Classes" table.

SELECT Students.Name, Classes.ClassName FROM Students INNER JOIN Classes ON Students.ClassID = Classes.ClassID;

7. Advanced SQL Queries

  • Subqueries: A query inside another query.

  • Common Table Expressions (CTE): A temporary result set used for complex queries.

  • Views: A virtual table that stores frequently used queries.

Example: Find students who have the highest age.

SELECT Name FROM Students WHERE Age = (SELECT MAX(Age) FROM Students);

8. Data Modification & Transactions

  • INSERT: Add new data.

  • UPDATE: Modify existing data.

  • DELETE: Remove data.

  • Transactions: A set of SQL operations that must succeed together.

Example: If updating student marks, either all updates should happen, or none should (to avoid incomplete changes).

START TRANSACTION; UPDATE Students SET Grade = 'A' WHERE ID = 1; COMMIT; -- Saves the changes

9. Indexing & Performance Optimization

  • Indexes speed up searches by organizing data efficiently.

  • Execution Plans help understand how SQL processes queries.

  • Optimization ensures that queries run faster.

Example: Creating an index on the "Name" column to speed up searches.

CREATE INDEX idx_student_name ON Students(Name);

10. Stored Procedures & Triggers

  • Stored Procedures: Predefined SQL scripts that can be reused.

  • Triggers: Automatic actions that happen when data is inserted, updated, or deleted.

Example: Create a stored procedure to update student grades.

CREATE PROCEDURE UpdateGrade (IN studentID INT, IN newGrade VARCHAR(5)) BEGIN UPDATE Students SET Grade = newGrade WHERE ID = studentID; END;

11. Working with NoSQL & Big Data (Optional)

SQL is great for structured data, but sometimes we need NoSQL databases like MongoDB when dealing with unstructured data.

SQL vs NoSQL:

  • SQL – Used for structured data (tables, rows, and columns).

  • NoSQL – Used for flexible and large-scale data storage (JSON, key-value pairs).

12. Real-Time SQL Project & Interview Preparation

  • Build a real-world SQL project, like an online bookstore database.

  • Practice interview questions such as:

    • What is the difference between DELETE and TRUNCATE?

    • Explain ACID properties in SQL.

    • How do you optimize SQL queries?

Report this page