SQL/Day1&Day2 at main · Rutujamhaske03/SQL · GitHub

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# 📘 SQL DAY 1 & DAY 2 NOTES

## 🟢 What is SQL?

- SQL stands for **Structured Query Language**
- Used to communicate with databases

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## 🟡 Data

**Data** is raw information that describes attributes of an entity.

**Examples:**
- Person: Name, Phone, DOB, Gender
- Laptop: Brand, RAM, Storage
- Bottle: Height, Color, Capacity

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## 🟠 Database

A **database** stores data in a systematic way.

**CRUD Operations:**
- Create / Insert
- Read / Retrieve
- Update / Modify
- Delete / Drop

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## 🔵 DBMS (Database Management System)

A software used to manage databases.

**Features:**
- Security
- Authorization

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## 🔴 RDBMS (Relational Database Management System)

Stores data in tables (rows & columns)

**Examples:**

| EMPNO | Name | Salary |
|-------|------|--------|
| 1     | A    | 5000   |
| 2     | B    | 6000   |

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## 🟣 Relational Model

- Proposed by **E.F. Codd**
- Forms the basis for RDBMS
- Follows rules (like data in tables, unique rows, etc.)

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## 🔘 Table

- Logical structure of rows (records) and columns (attributes)
- Smallest unit: **cell** (intersection of row and column)