# Data type in SQL

## 🧠 What are Data Types in SQL?

In SQL, **data types** define what **kind of data** can be stored in each column of a table—such as **numbers**, **text**, **dates**, or **true/false** values.

When you create a table, you must choose the correct data type for each column.

---

## 🔢 1. **Numeric Data Types**

Used to store numbers, like marks, price, quantity, etc.

| Data Type | Description | Example |
| --- | --- | --- |
| `INT` | Integer (whole numbers) | 100, -50 |
| `SMALLINT` | Smaller whole numbers | 300 |
| `BIGINT` | Very large whole numbers | 99999999999 |
| `DECIMAL(p,s)` | Exact decimal number, p = total digits, s = after decimal | DECIMAL(5,2) → 123.45 |
| `NUMERIC(p,s)` | Same as DECIMAL | NUMERIC(6,2) → 99.99 |
| `FLOAT` | Approximate decimal number | 3.14 |
| `REAL` | Less precision than FLOAT | 1.23 |

---

## 📝 2. **Character/String Data Types**

Used to store text like names, addresses, etc.

| Data Type | Description | Example |
| --- | --- | --- |
| `CHAR(n)` | Fixed length string, always uses `n` spaces | CHAR(5) → `'Hi '` |
| `VARCHAR(n)` | Variable length string (up to `n` characters) | VARCHAR(10) → `'Hello'` |
| `TEXT` | Large amount of text | `'This is a comment'` |

---

## 📅 3. **Date and Time Data Types**

Used to store date and/or time.

| Data Type | Description | Example |
| --- | --- | --- |
| `DATE` | Only date | `'2025-08-03'` |
| `TIME` | Only time | `'14:30:00'` |
| `DATETIME` | Both date and time | `'2025-08-03 14:30:00'` |
| `TIMESTAMP` | Like `DATETIME`, used in logs | `'2025-08-03 14:30:00'` |

---

## ✅ 4. **Boolean Data Type**

Stores **true/false** (yes/no) values.

| Data Type | Description | Example |
| --- | --- | --- |
| `BOOLEAN` | TRUE (1) or FALSE (0) | `TRUE` |

---

## 🧪 5. **Other Data Types (Special Use)**

| Data Type | Description | Example |
| --- | --- | --- |
| `BLOB` | Binary Large Object (files, images) | (used to store files) |
| `UUID` | Unique identifier | `'550e8400-e29b...'` |
| `JSON` | JSON formatted data | `'{"name": "Amit"}'` |

---

## 🧾 Example Table With Data Types

Here’s an example of a table that uses different types of data:

```sql
CREATE TABLE Students (
    StudentID INT PRIMARY KEY,         -- number (whole)
    Name VARCHAR(50),                  -- text
    DOB DATE,                          -- date
    Score DECIMAL(5,2),                -- number with decimal
    IsActive BOOLEAN                   -- true/false
);
```

This table will store:

* `StudentID`: Unique number for each student
    
* `Name`: Up to 50 characters
    
* `DOB`: Date of birth
    
* `Score`: Like marks (e.g., 88.75)
    
* `IsActive`: Whether the student is active or not (TRUE/FALSE)
    

---

## 📌 Quick Summary Table

| Category | Data Types |
| --- | --- |
| **Numeric** | INT, DECIMAL, FLOAT, BIGINT, SMALLINT |
| **Text** | CHAR, VARCHAR, TEXT |
| **Date/Time** | DATE, TIME, DATETIME, TIMESTAMP |
| **Boolean** | BOOLEAN |
| **Others** | JSON, UUID, BLOB |

### ✅ INSERT Commands (Add Rows)

Here are a few examples inserting different students:

```sql
INSERT INTO Students (StudentID, Name, DOB, Score, IsActive)
VALUES (1, 'Amit Singh', '2002-05-10', 89.75, TRUE);

INSERT INTO Students (StudentID, Name, DOB, Score, IsActive)
VALUES (2, 'Priya Sharma', '2001-11-22', 92.50, TRUE);

INSERT INTO Students (StudentID, Name, DOB, Score, IsActive)
VALUES (3, 'Rahul Mehta', '2003-03-15', 76.00, FALSE);

INSERT INTO Students (StudentID, Name, DOB, Score, IsActive)
VALUES (4, 'Anjali Verma', '2002-08-01', 84.25, TRUE);
```