In MySQL, a left join is used to combine all rows from the left table with matching rows from the right table based on a related column between them, and returns NULL for the columns from the right table where there is no matching row. The basic syntax for a left join in MySQL is:
SELECT columns FROM table1 LEFT JOIN table2 ON table1.column = table2.column;
In this syntax, columns are the columns you want to select from the combined tables, table1 is the left table and table2 is the right table you want to join, and column is the related column between the two tables.
Here’s an example of a left join between two tables:
SELECT orders.order_id, customers.customer_name FROM orders LEFT JOIN customers ON orders.customer_id = customers.customer_id;
In this example, the orders table and the customers table are joined using the customer_id column, but all records from the orders table are returned, even if there is no matching record in the customers table. If there is no matching record in the customers table, the customer_name column will be NULL.
For example, consider two tables, employees and departments, where the employees table has a column dept_id that relates to the departments table’s column dept_id. We can use a left join to get all the employees, along with their department names, even if there are no matching departments.
SELECT employees.employee_name, departments.department_name FROM employees LEFT JOIN departments ON employees.dept_id = departments.dept_id;
In this example, if there is no matching department for an employee, the department_name column will be NULL. This can be useful when you want to analyze employee data and
