What is the SELECT & FROM Clause in SQL: A Detailed Guide

SQL
June 24, 2024
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Introduction

If you’re new to SQL (Structured Query Language), one of the first things you’ll need to learn is how to retrieve data from a database. The SELECT and FROM clauses are fundamental components of SQL that allow you to do just that.

This blog will explain what these clauses are & how they work.

The SELECT Clause

The SELECT clause is used to specify which columns of data you want to retrieve from a table. Think of it as choosing the fields you want to see from a table.

Basic Syntax:

SELECT column1, column2, ...
FROM table_name;

Here,

column1, column2, …: The columns you want to retrieve.
table_name: The table from which you want to retrieve the data.

Example:

Imagine you have a table named Employees with the following structure:

To retrieve the first names and last names of all employees, you would use:

SELECT FirstName, LastName
FROM Employees;

This query would return:

The FROM Clause

The FROM clause specifies the table from which you want to retrieve data. It tells SQL where to look for the data you want to select.

Basic Syntax:

SELECT column1, column2, ...
FROM table_name;

Here, table_name is the name of the table from which you want to retrieve the data.

Example:

Continuing with the Employees table, if you want to retrieve all columns for all employees, you would use:

SELECT *
FROM Employees;

The asterisk (*) is a wildcard character that means “all columns.” This query would return:

Combining SELECT and FROM

The SELECT and FROM clauses are often used together to retrieve specific data from a table. You can specify exactly which columns you want to see and from which table.

To get the department and salary of each employee, you would use:

SELECT Department, Salary
FROM Employees;

This query would return:

Key Takeaways

SELECT Clause: Specifies the columns you want to retrieve from a table.
FROM Clause: Specifies the table from which to retrieve the data.
Wildcard (*): Used in the SELECT clause to retrieve all columns from a table.
Aliases: Temporary names given to columns or tables for easier readability.
Basic SQL Syntax: