What is join in mysql

JOIN in MySQL is a query command used to combine data from different tables by creating a temporary table by matching columns. There are four types of JOIN: INNER JOIN (matches only rows that exist in both tables), LEFT JOIN (selects all rows in the left table), RIGHT JOIN (selects all rows in the right table), and FULL JOIN (selects all rows in both tables). JOIN improves efficiency and readability by combining data, avoiding subqueries, simplifying queries, and more.

What is JOIN in MySQL

JOIN is a query in MySQL used to combine data from different tables Order. It creates temporary tables by comparing matching columns in two or more tables, allowing us to retrieve data from multiple tables.

Types of JOIN

There are four main JOIN types, each combining data in a different way based on matching conditions:

• INNER JOIN: Select only records that have matching rows in all joined tables.
• LEFT JOIN: Selects all records in the left table, even if they have no matching rows in the right table.
• RIGHT JOIN: Selects all records in the right table, even if they have no matching rows in the left table.
• FULL JOIN (or FULL OUTER JOIN): Selects all records from the left and right tables, even if they have no matching rows in the other table.

JOIN syntax

The following is the syntax of an INNER JOIN query:

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

• SELECT: Specify the columns to retrieve.
• FROM: Specify the table to be connected.
• INNER JOIN: Specify the JOIN type.
• ON: Specify the connection conditions.

Benefits of JOIN

JOIN is very useful because it allows us to:

• Combine data from multiple tables.
• Avoid subqueries to improve performance.
• Simplify complex queries to make them easier to understand.

Example

Consider the following two tables:

• Customer table: contains customer information, Such as customer ID, name, address.
• Order table: Contains order information, such as order ID, customer ID, product name.

We can use JOIN to get each customer and their order information:

<code class="sql">SELECT *
FROM customers
INNER JOIN orders
ON customers.customer_id = orders.customer_id;</code>

The result will contain the following data:

customer_id	name	address	order_id	product_name
1	John Doe	123 Main St	100	Product A
1	John Doe	123 Main St	200	Product B
2	Jane Smith	456 Elm St	300	Product C

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