Working with Data

You have learned how Subqueries works in the previous article. Now it’s time to explore how to insert, modify and delete data in your tables. This is where SQL becomes a powerful tool for maintaining and managing your database.

Let’s walk through how to add, change, and remove data with clear examples using SQL Server.

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Inserting Data into Tables

Adding new data to a table is done using the INSERT statement. Think of it as adding a new row to your spreadsheet.

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Syntax:

INSERT INTO table_name (column1, column2, ...)  
VALUES (value1, value2, ...);  

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Example: Adding a New Product

Imagine you’ve just launched a new product, “Fitness Band,” and want to add it to the Products table.

INSERT INTO products (product_id, product_name, category, price, stock)  
VALUES (6, 'Fitness Band', 'Fitness', 3500, 20);  

Result: A new row is added to the table:

This is how simple it is to add new data!

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Updating Data in Tables

What if your inventory changes, and you need to update the quantity of products in stock? That’s where the UPDATE statement comes in.

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Syntax:

UPDATE table_name  
SET column1 = value1, column2 = value2, ...  
WHERE condition;  

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Example: Restocking a Product

Suppose a new shipment of Yoga Mats arrives, and you need to increase their stock by 30 units.

UPDATE products  
SET stock = stock + 30  
WHERE product_name = 'Yoga Mat';  

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Result: The stock for “Yoga Mat” is updated:

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Deleting Data from Tables

Sometimes, you’ll need to remove outdated or incorrect data. For this, you use the DELETE statement.

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Syntax:

DELETE FROM table_name  
WHERE condition;  

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Example: Removing a Discontinued Product

Let’s say the “Wireless Mouse” is no longer sold. Here’s how you can remove it from the Products table:

DELETE FROM products  
WHERE product_name = 'Wireless Mouse';  

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Result: The “Wireless Mouse” is gone from the table.

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Scenario: Managing Inventory

Let’s tie everything together with a realistic example:

1. Adding a new product:
   You receive a new product, “Treadmill,” and want to add it to the database:

INSERT INTO products (product_id, product_name, category, price, stock)  
VALUES (7, 'Treadmill', 'Fitness', 45000, 5);  

2. Updating existing stock:
   A shipment of “Bluetooth Speakers” arrives, so you increase their stock by 10 units:

UPDATE products  
SET stock = stock + 10  
WHERE product_name = 'Bluetooth Speaker';  

3. Removing a discontinued product:
   The “Smartwatch” is discontinued, so you delete it from the table:

DELETE FROM products  
WHERE product_name = 'Smartwatch';  

These commands together allow you to fully manage the data in your tables.

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Summary

• Use INSERT to add new rows to your tables.
• Use UPDATE to modify existing data, but always double-check your WHERE clause to avoid accidental updates.
• Use DELETE to remove rows, but be cautious—deleting without a WHERE clause removes all rows in the table.

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What’s Next?

Now that you’ve mastered modifying data, the next step is to learn about creating and altering tables. Stay tuned!