Operators in SQL: Relational and Logical

What is an Operator?

An operator in SQL is like a special symbol or word that helps you perform actions on data in a database. Think of them as the tools you use to work with data.

Relational Operators

Relational operators are used to compare values in SQL. They help us answer questions like “Is this value bigger than that value?” or “Are these two values equal?”

Here are some common relational operators:

Operator	Meaning
=	Equal
<> or !=	Not Equal
<	Less Than
>	Greater Than
<=	Less Than or Equal To
>=	Greater Than or Equal To

For example, you might use = to check if a student’s age is equal to 18.

Logical Operators

Logical operators, on the other hand, help us combine conditions or statements in SQL. They allow us to ask more complex questions.

Here are the main logical operators:

Operator	Meaning
AND	Both conditions must be true
OR	At least one condition must be true
NOT	Inverts a condition (true becomes false and vice versa)

For instance, you can use AND to check if a customer’s age is greater than 18 and they have a valid ID.

In Brief

• Operators in SQL are tools for working with data.
• Relational operators compare values, like checking if two values are equal.
• Logical operators combine conditions, allowing us to ask complex questions.
• Common relational operators include =, <> (or !=), <, >, <=, and >=.
• Key logical operators are AND, OR, and NOT.

Understanding Special Operators and SQL Operators

In SQL, there are special operators and SQL operators that help us manipulate and retrieve data from a database. Let’s break down what these operators do with easy-to-understand explanations, examples, and a summary in a table format.

Special Operators

1. BETWEEN Operator

• The BETWEEN operator is used to filter data within a specified range.
• It includes the values you specify in the range.
• Syntax: column_name BETWEEN value1 AND value2

Example:

SELECT * FROM products WHERE price BETWEEN 10 AND 50;

2. IN Operator

• The IN operator is used to match a value against a list of values.
• It is handy when you want to filter data from a predefined set of values.
• Syntax: column_name IN (value1, value2, ...)

Example:

SELECT * FROM employees WHERE department IN ('HR', 'IT', 'Finance');

3. LIKE Operator

• The LIKE operator is used for pattern matching with wildcard characters (% and _).
• It helps find data that matches a specific pattern.
• Syntax: column_name LIKE 'pattern'

Example:

SELECT * FROM customers WHERE email LIKE '%gmail.com';

4. IS NULL Operator

• The IS NULL operator is used to check if a column contains NULL values.
• It helps identify records with missing data.
• Syntax: column_name IS NULL

Example:

SELECT * FROM orders WHERE ship_date IS NULL;

SQL Operators

1. Comparison Operators

• These operators (e.g., =, <, >, <=, >=) are used to compare values in SQL queries.
• They help filter and retrieve data based on specific conditions.
• Syntax: column_name operator value

Example:

SELECT * FROM products WHERE price > 50;

2. Logical Operators

• Logical operators (e.g., AND, OR, NOT) are used to combine conditions in SQL queries.
• They help create complex filtering criteria.
• Syntax: condition1 AND/OR/NOT condition2

Example:

SELECT * FROM employees WHERE department = 'HR' AND salary > 40000;

3. Arithmetic Operators

• Arithmetic operators (e.g., +, -, *, /) are used for mathematical calculations in SQL.
• They allow you to perform calculations on numeric data.
• Syntax: value1 operator value2

Example:

SELECT product_name, price * 1.1 AS updated_price FROM products;

4. Assignment Operator (=)

• The assignment operator is used to update the value of a column in an SQL query.
• It assigns a new value to a column.
• Syntax: UPDATE table_name SET column_name = new_value WHERE condition

Example:

UPDATE employees SET salary = salary * 1.05 WHERE department = 'Finance';

Summary in Table Format

Operator	Description	Example
BETWEEN	Filters data within a specified range	price BETWEEN 10 AND 50
IN	Matches a value against a list of values	department IN ('HR', 'IT', 'Finance')
LIKE	Matches data based on a pattern	email LIKE '%gmail.com'
IS NULL	Checks for NULL values in a column	ship_date IS NULL
Comparison	Compares values in SQL queries	price > 50
Logical	Combines conditions for complex filtering	department = 'HR' AND salary > 40000
Arithmetic	Performs mathematical calculations	price * 1.1 AS updated_price
Assignment (=)	Updates the value of a column in SQL queries	SET salary = salary * 1.05 WHERE department = 'Finance'

Understanding these operators is essential for crafting precise and efficient SQL queries to retrieve and manipulate data from databases.