Basic SELECT Query

The SELECT statement is the most commonly used SQL command. It is used to retrieve data from one or more tables in a database.

Once you have inserted data into a table, you use SELECT queries to view, analyze, and report that data.

Basic Syntax

SELECT column1, column2, ...
FROM table_name;

• SELECT: specifies which columns you want to retrieve
• FROM: specifies the table from which to retrieve the data

Example Table: students

CREATE TABLE students (
  id INT PRIMARY KEY,
  name VARCHAR(100),
  age INT,
  email VARCHAR(150),
  enrollment_date DATE
);

Assume we have inserted some data into the students table:

INSERT INTO students (id, name, age, email, enrollment_date)
VALUES
  (1, 'Alice Smith', 20, 'alice@example.com', '2025-06-23'),
  (2, 'Bob Johnson', 22, 'bob@example.com', '2025-06-20'),
  (3, 'Carol Thomas', 19, 'carol@example.com', '2025-06-21');

Example 1: Select All Columns

SELECT * FROM students;

• The * symbol means “all columns”.
• This query retrieves all columns and all rows from the students table.

Result:

Example 2: Select Specific Columns

You can retrieve only the columns you need:

SELECT name, age FROM students;

Result:

Example 3: Rename Columns (Alias)

You can rename columns in your result using AS:

SELECT name AS student_name, age AS student_age
FROM students;

Result:

Example 4: Simple Calculations

You can perform basic calculations:

SELECT name, age + 1 AS next_year_age
FROM students;

This shows each student’s age next year.

Important Notes

• Every SQL query must end with a semicolon (;).
• Column names in SELECT can appear in any order.
• You can mix columns and expressions in the same query.

Summary

• SELECT is used to retrieve data from a table.
• SELECT * retrieves all columns.
• You can select only specific columns.
• You can rename columns and perform basic calculations in your queries.
• SELECT is the foundation of all data retrieval in SQL.