SQL SELECT: The Essential Guide for Beginners

Learn how to use the SQL SELECT statement to retrieve data from databases. This tutorial will teach you the basics of SELECT syntax, including how to specify columns, filter results, and sort data. With SQL SELECT, you can get the data you need to answer your questions and make informed decisions. 

The SQL SELECT statement is used to select (retrieve) data from a database table.

Example

-- select first_name from Customers table 
SELECT first_name
FROM Customers;

The above SQL query selects the first_name of all the customers from the Customers table.

SQL SELECT Syntax

The syntax of the SQL SELECT statement is:

SELECT column1, column2, ...
FROM table;

Here,

• column1, column2, ... are the table columns
• table is the table name from where we select the data

For example,

-- select first_name and last_name columns from Customers table 
SELECT first_name, last_name
FROM Customers;

Here, the SQL command selects the first_name and last_name of all customers in the Customers table.

Example: SQL SELECT

SQL SELECT ALL

To select all columns from a database table, we use the * character. For example,

-- select all columns from Customers table 
SELECT *
FROM Customers;

Here, the SQL command selects all columns of the Customers table.

Example: SQL SELECT All

SQL SELECT WHERE Clause

A SELECT statement can have an optional WHERE clause. The WHERE clause allows us to fetch records from a database table that matches specified condition(s). For example,

-- select all columns from the customers table with last_name 'Doe' 
SELECT *
FROM Customers
WHERE last_name = 'Doe';

Here, the SQL command selects all customers from the Customers table with the last_name Doe.

Example: SQL SELECT with WHERE

Let's look at another example.

-- select age and country columns from customers table where the country is 'USA' 
SELECT age, country
FROM Customers
WHERE country = 'USA';

Here, the SQL command selects the age and country columns of all the customers whose country is USA.

Example: SQL SELECT with WHERE

We can also use the WHERE clause with the UPDATE statement to edit existing rows in a database table.

Note: In SQL, we must enclose textual data inside either single or double quotations like 'USA'.

SQL Operators

The WHERE clause uses operators to construct conditions. Some of the commonly used operators are:

1. Equal to Operator (=)

-- select all columns from Customers table with first name 'John'
SELECT *
FROM Customers
WHERE first_name = 'John';

The above SQL command selects all the customers from the Customers table having first_name John.

2. Greater than (>)

-- select all columns from Customers table with age greater than 25
SELECT *
FROM Customers
WHERE age > 25;

The above SQL command selects all the customers from the Customers table whose age is greater than 25.

3. AND Operator (AND)

-- select all columns from Customers table with last_name 'Doe' and country 'USA'
SELECT *
FROM Customers
WHERE last_name = 'Doe' AND country = 'USA';

The above SQL command selects all the customers from the Customers table having last_name Doe and country USA.

Note: If none of the rows meet the WHERE clause condition, an empty result set is returned.

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