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tutorial/first-query.spec
Write Your First SQL Query
This tutorial teaches you SQL basics using SQL Developer. You'll learn SELECT, WHERE, ORDER BY, and JOIN — the building blocks of every database query.
# Tutorial
level = Beginner
time = 15 minutes
topics = SELECT · WHERE · ORDER BY · LIMIT · JOIN
prereq = SQL Developer + a database connection
# Examples
dialects = MySQL · PostgreSQL · Oracle · SQL Server · SQLite
tables_used = customers · orders · products
// includes a practice exercise at the end
step/open-editor.txt
Opening the Query Editor
After you download SQL Developer and connect to your database, you're ready to write queries.
- In the Connections panel, right-click your connection
- Select Open SQL Worksheet
- A new query tab opens with a blank editor
Keyboard shortcut: Press Ctrl + N to open a new query window.
topic/select.sql
The SELECT Statement
SELECT retrieves data from your database. It's the most common SQL command you'll use.
Select All Columns
Use * to select every column from a table:
SELECT * FROM customers;
Select Specific Columns
List the column names you want to retrieve:
SELECT first_name, last_name, email
FROM customers;
Running Your Query
- Run Statement — press
Ctrl + Enter— runs the current statement - Run Script — press
F5— runs all statements in the editor
Results appear in the panel below the editor.
topic/where.sql
Filtering with WHERE
The WHERE clause filters results to show only rows that match your conditions.
SELECT * FROM orders
WHERE total_amount > 100;
SELECT * FROM customers
WHERE country = 'USA';
-- Both conditions must be true
SELECT * FROM products
WHERE category = 'Electronics' AND price < 500;
-- Either condition can be true
SELECT * FROM customers
WHERE country = 'USA' OR country = 'Canada';
-- Names starting with 'J'
SELECT * FROM customers
WHERE first_name LIKE 'J%';
-- Email addresses from gmail
SELECT * FROM customers
WHERE email LIKE '%@gmail.com';
% matches any number of characters. _ matches exactly one character.
topic/order-by.sql
Sorting with ORDER BY
ORDER BY sorts your results in ascending (ASC) or descending (DESC) order.
SELECT * FROM products
ORDER BY price;
SELECT * FROM products
ORDER BY price DESC;
SELECT * FROM customers
ORDER BY country ASC, last_name ASC;
This sorts first by country, then by last name within each country.
topic/limit.sql
Limiting Results
When working with large tables, limit the number of rows returned. Syntax differs by database.
SELECT * FROM orders
ORDER BY order_date DESC
LIMIT 10;
-- Oracle 12c and later (preferred)
SELECT * FROM orders
ORDER BY order_date DESC
FETCH FIRST 10 ROWS ONLY;
-- Older Oracle
SELECT * FROM orders
WHERE ROWNUM <= 10
ORDER BY order_date DESC;
SELECT TOP 10 * FROM orders
ORDER BY order_date DESC;
topic/join.sql
Combining Tables with JOIN
JOIN combines rows from two or more tables based on a related column.
INNER JOIN
Returns only rows that have matching values in both tables:
SELECT orders.order_id, customers.first_name, orders.total_amount
FROM orders
INNER JOIN customers ON orders.customer_id = customers.customer_id;
Using Table Aliases
Make your queries shorter and more readable:
SELECT o.order_id, c.first_name, c.last_name, o.total_amount
FROM orders o
INNER JOIN customers c ON o.customer_id = c.customer_id
WHERE o.total_amount > 100
ORDER BY o.order_date DESC;
LEFT JOIN
Returns all rows from the left table, even if there's no match in the right table:
SELECT c.first_name, c.last_name, o.order_id
FROM customers c
LEFT JOIN orders o ON c.customer_id = o.customer_id;
Customers without orders will show NULL for order columns.
practice/exercise.txt
Practice Exercise
Try writing these queries in SQL Developer to lock in what you learned.
- Select all customers from your database
- Find customers whose email contains "gmail"
- List the 5 most recent orders
- Show all orders with customer names (using JOIN)
- Find orders over $100 from customers in the USA
Tip: Use Ctrl + Space in SQL Developer for auto-complete suggestions as you type table and column names.
whats-next.txt
Next Steps
Continue learning with these related guides.
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Format SQL
Auto-format messy SQL into clean, readable code with Ctrl+F7.
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Run SQL Scripts
Execute .sql files and multiple queries with F5.
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