Hey there! If you're diving into the world of databases, SQL (Structured Query Language) is your golden ticket to handle and manipulate data. It's like learning the secret handshake to the programming club. In this article, I'll share the top 10 SQL commands that every programmer should have in their toolbox.
10 SQL commands every Programmer should learn
1. SELECT
First up, we have the SELECT command. It's your data detective tool. With SELECT, I can fetch data from a table. For instance, "SELECT * FROM customers" fetches all rows from the "customers" table.
SELECT is your starting point in SQL. It's how you fetch data from one or more tables. Whether you want all columns or specific ones, SELECT is your go-to move. For instance:
SELECT * FROM customers;
2. INSERT
When you want to add new data to your table, INSERT comes to the rescue. It's like adding new tracks to your playlist. I can do something like "INSERT INTO employees (name, age) VALUES ('John', 30)" to add a new employee.
This query retrieves all rows from the "customers" table, displaying all columns. It's like asking your DJ to play every track from your favorite album.
INSERT INTO employees (name, age) VALUES ('John', 30);
3. UPDATE
Ever needed to change existing data? UPDATE lets you give it a makeover. Like changing the cover art of your favorite album, "UPDATE products SET price = 19.99 WHERE product_id = 123" updates the price of a product.
Sometimes, your data needs a makeover. That's where UPDATE comes in. It's like giving your favorite track a fresh remix. Here's how it's done:
UPDATE products SET price = 19.99 WHERE product_id = 123;
4. DELETE
DELETE is your data cleanup tool. Just as you skip a song you don't like, you can use DELETE to remove unwanted data. For example, "DELETE FROM orders WHERE order_id = 456" removes a specific order.
DELETE is your cleanup crew. It's how you remove unwanted data from your table. Just as you'd skip a song you don't like, you can use DELETE to get rid of data you no longer need. Here's an example:
DELETE FROM orders WHERE order_id = 456;
5. CREATE TABLE
To create a new table, you've got CREATE TABLE. It's like designing a new stage for your concert. For instance, "CREATE TABLE movies (id INT, title VARCHAR(255), year INT)" sets up a "movies" table with columns for ID, title, and year.
Creating a new table? CREATE TABLE is your building block. It's like designing a new stage for your concert. Here's how you set it up:
CREATE TABLE movies (id INT, title VARCHAR(255), year INT);
6. ALTER TABLE
Sometimes, you need to tweak your table's structure. ALTER TABLE comes in handy. It's like adjusting the sound levels at a live show. I can use it to add, modify, or delete columns in an existing table.
As your show evolves, you might need to tweak the stage setup. ALTER TABLE lets you modify an existing table's structure. It's like adjusting the sound levels at a live performance. You can use it to add, modify, or delete columns. Here's an example:
ALTER TABLE customers ADD COLUMN phone_number VARCHAR(20);
7. DROP TABLE
When you're done with a table and want to remove it entirely, DROP TABLE is your cleanup crew. It's like packing up the stage after the concert. "DROP TABLE old_data" will remove the "old_data" table from your database.
When the concert's over, and you're ready to pack up the stage, DROP TABLE comes in handy. It's how you remove an entire table from your database. Here's how it's done:
DROP TABLE old_data;
8. JOIN
Data from multiple tables? JOIN is your superhero, uniting them. Think of it as a musical collaboration. INNER JOIN, LEFT JOIN, RIGHT JOIN, or FULL JOIN, use the one that fits your data duet.
Data from multiple tables? JOIN is your superhero, uniting them like a musical collaboration. Whether it's INNER JOIN, LEFT JOIN, RIGHT JOIN, or FULL JOIN, you choose the one that fits your data duet.
For example, if you want to combine data from an "orders" table with customer information from a "customers" table, you can use INNER JOIN:
SELECT orders.order_id, customers.customer_name FROM orders INNER JOIN customers ON orders.customer_id = customers.customer_id;
9. GROUP BY
GROUP BY is like your event planner. It organizes data into groups. Just as you'd categorize songs by genre, you can group data by a specific column and apply aggregate functions to each group.
GROUP BY is like your event planner. It's how you organize data into groups, just as you'd categorize songs by genre. You can group data by a specific column and then apply aggregate functions to each group.
For instance, if you have a "sales" table and you want to calculate the total sales for each product category:
SELECT category, SUM(amount) AS total_sales FROM sales GROUP BY category;
10. ORDER BY
To sort your data like a DJ arranges tracks in a playlist, you've got ORDER BY. You can sort results in ascending (ASC) or descending (DESC) order based on a column.
To sort your data like a DJ arranges tracks in a playlist, you've got ORDER BY. It helps you arrange your results in ascending (ASC) or descending (DESC) order based on a specific column.
For example, if you want to sort a list of products by price in descending order:
SELECT product_name, price FROM products ORDER BY price DESC;
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