Retrieving Data from Tables (SELECT)

Welcome back, future SQL experts! Now that you know how to insert data into a table, the next step is learning how to retrieve that data.

In this chapter, we’ll cover:

• The basic SELECT statement
• Selecting specific columns
• Using WHERE to filter results
• Aliasing columns
• Sorting with ORDER BY
• Real examples using our students table

Let’s dive in! 🚀

🧠 Why SELECT is Important

The SELECT statement is the most commonly used command in SQL. Whether you're displaying a report, fetching records for analysis, or just checking if your data was saved properly — you'll use SELECT .

✅ Syntax

 SELECT column1, column2, ... FROM table_name; 

To get all columns from a table:

 SELECT * FROM table_name; 

🧪 Example Table: students

Let's continue using our sample table:

 CREATE TABLE students 
( id INT , 
name VARCHAR ( 50 ), 
age INT , 
course VARCHAR ( 30 ), 
marks DECIMAL ( 5 , 2 )); 

And here are some sample rows:

id	name	age	course	marks
1	Rahul Sharma	21	SQL	85.50
2	Anjali Mehta	22	SQL	91.75
3	Vikas Gupta	23	SQL	88.00

🔍 Select All Records

 SELECT * FROM students; 

This will return all columns and rows in the table.

🎯 Select Specific Columns

 SELECT name, marks FROM students; 

This shows only the student names and their marks.

🎛 Filter Results with WHERE

  SELECT * FROM students WHERE marks > 85 ; 

This will show only students who scored more than 85 marks.

More filter examples:

 SELECT name FROM students 
WHERE age = 22 ; 

SELECT * FROM students 
WHERE course = 'SQL' AND marks > 90 ; 

🏷 Use Aliases with AS

Aliases help rename columns for readability:

 SELECT name AS "Student Name", marks AS "Score" FROM students; 

🔢 Sorting Results with ORDER BY

 SELECT * FROM students ORDER BY marks DESC ; 

• ASC : Ascending (default)
• DESC : Descending

You can also sort by multiple columns:

 SELECT * FROM students ORDER BY course, name; 

📌 Practice Tasks

Try writing queries for these:

1. Show names and marks of students who scored above 90.
2. Show all students sorted by age, oldest first.
3. Display all students who are enrolled in "SQL" and are younger than 23.

Post your answers in the blog comments! I’ll review them. 😊

🚧 Common Mistakes

Mistake	Issue
SELECT name, age students;	Missing FROM keyword
SELECT * FROM table;	Incorrect table name
WHERE age = 'twenty'	Wrong data type in condition

📌 Summary

Task	SQL Example
Select all columns	SELECT * FROM students;
Select specific columns	SELECT name, marks FROM students;
Use filters	WHERE age >20
Sort results	ORDER BY marks DESC
Rename columns	AS keyword