What are some examples of SQL joins?

What are some examples of SQL joins?

SQL joins are used to combine rows from two or more tables based on a related column. Here are some examples:

1. INNER JOIN: Returns records that have matching values in both tables.
2. LEFT JOIN: Returns all records from the left table and matched records from the right table.
3. RIGHT JOIN: Returns all records from the right table and matched records from the left table.
4. FULL OUTER JOIN: Returns all records when there is a match in either left or right table records.

Can you give me a specific example of an INNER JOIN?

Sure! Suppose we have two tables: employees and departments. An INNER JOIN can be used to get a list of employees along with their department names:

SELECT employees.name, departments.department_name
FROM employees
INNER JOIN departments ON employees.department_id = departments.id;

What about a LEFT JOIN example?

Absolutely! Using the same employees and departments tables, a LEFT JOIN would look like this:

SELECT employees.name, departments.department_name
FROM employees
LEFT JOIN departments ON employees.department_id = departments.id;

This will return all employees, and if an employee does not belong to a department, the department name will be NULL.

Thanks! What are the differences between these joins?

The main differences are:

• INNER JOIN: Only returns rows with matching values in both tables.
• LEFT JOIN: Returns all rows from the left table and matched rows from the right table, filling in NULLs where there are no matches.
• RIGHT JOIN: Similar to LEFT JOIN but returns all rows from the right table.
• FULL OUTER JOIN: Combines the results of both LEFT and RIGHT joins.