What is SQL?
SQL stands for Structured Query Language.
It's how you talk to a database. You write commands, and the database gives you data.
Your First SQL Command
Here's the simplest SQL command:
SELECT * FROM students;What does this mean?
- SELECT = "Show me"
- ***** = "everything"
- FROM = "from this table"
- students = the table name
- ; = end of command
In simple English: "Show me everything from the students table"
The Basic Pattern
Every SQL command follows this pattern:
SELECT (what you want) FROM (which table)
Examples:
SELECT * FROM students;
SELECT name FROM students;
SELECT name, age FROM students;3 Simple Rules
Rule 1: End every command with semicolon (;)
Rule 2: SQL keywords (SELECT, FROM) can be uppercase or lowercase
Rule 3: Spaces don't matter - write it however you like
These are all the same:
SELECT * FROM students;
select * from students;
SELECT *
FROM students;Common Mistakes to Avoid
Forgetting the semicolon:
SELECT * FROM students -- Wrong!
SELECT * FROM students; -- Correct!Misspelling keywords:
SELCT * FROM students; -- Wrong!
SELECT * FROM students; -- Correct!Try It Yourself!
Use the playground below to run your first SQL command.
What's Next?
You just wrote your first SQL command! Next, let's learn the most important SQL keywords.
Question 1: Show all students from the table
Write a query to display all columns and all rows from the students table.
Click "Run Query" to see results
Question 2: Show only name and age
Modify the query to show only the name and age columns. Try changing "age" to "grade" and run again!
Click "Run Query" to see results