What is SELECT

The SELECT statement is used to retrieve data from a table. It is the most fundamental SQL command and is used in almost every query.

Basic Syntax

sql
SELECT column1, column2
FROM table_name;

• SELECT specifies the columns to retrieve
• FROM specifies the table

Example Dataset

Table: employees

Selecting All Columns

sql
SELECT * FROM employees;

This retrieves all columns and all rows from the table.

Selecting Specific Columns

sql
SELECT name, salary FROM employees;

This retrieves only the name and salary columns.

Column Order Matters

sql
SELECT salary, name FROM employees;

The output will display columns in the same order as written in the query.

Using Aliases (Renaming Columns)

sql
SELECT name AS employee_name, salary AS income
FROM employees;

• AS is used to rename columns in the output
• Useful for readability and reporting

Removing Duplicate Values with DISTINCT

sql
SELECT DISTINCT department FROM employees;

This returns only unique department values.

Key Concepts

• SELECT * is useful for exploration but not recommended in production
• Always select only required columns for efficiency
• Use DISTINCT when you need unique values
• Use aliases to make results clearer