PostgreSQL Less Than Operator

PostgreSQL Less Than Operator

The PostgreSQL < operator is used to compare whether one expression is less than another. This operator is essential for filtering query results based on a comparison that checks if a specified column or expression is less than a given value.

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Syntax

SELECT columns
FROM table_name
WHERE column < value;

The < operator has the following components:

• columns: The columns to be retrieved from the table.
• table_name: The table from which to retrieve the data.
• column: The column to be compared.
• value: The value to compare against.

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Example PostgreSQL Less Than Queries

Let's look at some examples of PostgreSQL < operator queries:

1. Basic Less Than Example

SELECT customer_id, customer_name
FROM customers
WHERE customer_id < 3;

This query retrieves the customer_id and customer_name from the customers table where the customer_id is less than 3.

2. Less Than with Numeric Comparison

SELECT product_id, product_name
FROM products
WHERE price < 50.00;

This query retrieves the product_id and product_name from the products table where the price is less than 50.00.

3. Less Than with Date Comparison

SELECT order_id, order_date
FROM orders
WHERE order_date < '2024-01-01';

This query retrieves the order_id and order_date from the orders table where the order_date is earlier than '2024-01-01'.

4. Less Than with String Comparison

SELECT customer_id, customer_name
FROM customers
WHERE customer_name < 'M';

This query retrieves the customer_id and customer_name from the customers table where the customer_name is alphabetically less than 'M'.

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Full Example

Let's go through a complete example that includes creating a table, inserting data, and using the Less Than operator to filter data.

Step 1: Creating a Table

This step involves creating a new table named products to store product data.

CREATE TABLE products (
    product_id SERIAL PRIMARY KEY,
    product_name VARCHAR(100),
    price NUMERIC(10, 2)
);

In this example, we create a table named products with columns for product_id, product_name, and price.

Step 2: Inserting Data into the Table

This step involves inserting some sample data into the products table.

INSERT INTO products (product_name, price)
VALUES ('Product A', 30.00),
       ('Product B', 60.00),
       ('Product C', 90.00);

Here, we insert data into the products table.

Step 3: Using the Less Than Operator

This step involves using the < operator to filter data from the products table.

-- Basic Less Than
SELECT product_id, product_name
FROM products
WHERE price < 50.00;

-- Less Than with Numeric Comparison
SELECT product_id, product_name
FROM products
WHERE price < 50.00;

-- Less Than with Date Comparison
SELECT order_id, order_date
FROM orders
WHERE order_date < '2024-01-01';

-- Less Than with String Comparison
SELECT customer_id, customer_name
FROM customers
WHERE customer_name < 'M';

These queries demonstrate how to use the < operator to filter data from the products table, including basic numeric comparisons, date comparisons, and string comparisons.

Conclusion

The PostgreSQL < operator is a fundamental tool for comparing whether one expression is less than another. Understanding how to use the < operator and its syntax is essential for effective data retrieval and manipulation in PostgreSQL databases.