How to use inner join in mysql

INNER JOIN is an operation that joins tables and returns only rows with matching records in the two tables. It is used to correlate records from different tables, filter and obtain specific data, and create complex queries. When using it, you need to specify the connection conditions, that is, the matching columns between the two tables. This operation returns only matching rows, unmatched rows are filtered out.

Usage of INNER JOIN in MySQL

Definition:
INNER JOIN is A query operation that joins two tables and returns only rows with matching records in both tables.

Syntax:

<code class="sql">SELECT column_list
FROM table1
INNER JOIN table2 ON table1.column_name = table2.column_name;</code>

Usage:
INNER JOIN is used to retrieve related data from multiple tables. When two tables Used when there are columns in common between records, thereby establishing a relationship and returning only rows with matching records.

Usage scenarios:

• Associate records in different tables, such as obtaining order information from the customer table.
• Filter and get specific data from multiple tables, such as filtering out orders with a specific status.
• Create complex queries to join multiple tables and return specific results.

Example:

Suppose we have two tables, customers and orders:

customers		orders
id		id
name		customer_id
city		product_name
	quantity

To get each customer’s order quantity, we can use INNER JOIN:

<code class="sql">SELECT c.name, COUNT(o.product_name) AS order_count
FROM customers c
INNER JOIN orders o ON c.id = o.customer_id
GROUP BY c.name;</code>

Note points:

• INNER JOIN ensures that only rows with matching records in both tables are returned, no matching rows will be filtered out.
• The join condition specifies the matching columns between the two tables.
• You can use multiple connection conditions to specify more complex connection relationships.

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