SQL INNER JOIN

SQL INNER JOIN retrieves records from two tables based on a related column, returning only the rows where there is a match in both tables.

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1. Overview

SQL INNER JOIN is used to combine rows from two or more tables based on a related column between them. It returns only the rows where there is a match in both tables, discarding rows where no matching relationship exists.

Example:

// Example of using INNER JOIN to retrieve data from two tables
SELECT customers.customer_name, orders.order_date
FROM customers
INNER JOIN orders ON customers.customer_id = orders.customer_id;

This example retrieves the customer names along with their order dates, including only those customers who have placed orders.

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2. Syntax

The syntax for SQL INNER JOIN is as follows:

SELECT columns
FROM table1
INNER JOIN table2 ON table1.column = table2.column;

Where table1 and table2 are the tables to be joined, and column is the related column that exists in both tables.

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3. Usage

SQL INNER JOIN is commonly used to retrieve data that exists in both tables based on a related column. It is useful for performing queries that require data from multiple tables with a matching relationship.

Example:

// Example of using INNER JOIN to retrieve matching records from two tables
SELECT customers.customer_name, orders.order_date
FROM customers
INNER JOIN orders ON customers.customer_id = orders.customer_id;

This example retrieves customer names along with their order dates, including only those customers who have placed orders.

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4. Conclusion

SQL INNER JOIN is a fundamental operation in database querying, allowing users to retrieve data from multiple tables based on a common relationship. By combining rows from different tables, INNER JOIN facilitates comprehensive data analysis and reporting.