SQL Multi-Table Join Query 3 Tables

By joining multiple tables using a JOIN clause, grouping rows together according to common columns or expressions. Determine a common column or expression: Identifies the common column or expression to join the table. Specify the join type: Select INNER JOIN (match rows), LEFT JOIN (including all rows in the left table), RIGHT JOIN (including all rows in the right table), or FULL JOIN (including all rows in the right table). Use JOIN statement: Use JOIN statement to join tables together and match rows based on common columns or expressions.

SQL Multi-table Join Query 3 Tables

How to perform multi-table join query?

By using the JOIN clause, you can join multiple tables. The JOIN clause combines rows in a table based on a common column or expression.

step:

1. Determine common column or expression: Determines the common column or expression to join the table.
2. Specify connection type: Specify connection type (INNER JOIN, LEFT JOIN, RIGHT JOIN, or FULL JOIN).
3. Use JOIN statement: Use JOIN statement to join tables together.

Example:

Example query that connects 3 tables (customer, order, and product):

 <code class="sql">SELECT * FROM customers AS c INNER JOIN orders AS o ON c.customer_id = o.customer_id INNER JOIN products AS p ON o.product_id = p.product_id;</code>

Connection type:

• INNER JOIN: Return only rows with common values ​​in both tables.
• LEFT JOIN: Returns all rows in the left table, even if there is no match in the right table.
• RIGHT JOIN: Returns all rows in the right table, even if there is no match in the left table.
• FULL JOIN: Returns all rows in both tables, even if there is no match.

Other notes:

• The join order is important because the rows in the first table will match the rows in the second table, and so on.
• Multiple tables can be joined using multiple JOIN clauses.
• JOIN statements can use alias to simplify table and column references.

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