SQL JOINS are a fundamental part of any database query language. They are used to combine data from multiple tables into one result set. A join is a clause in an SQL statement that indicates how two or more tables are related.

Joins can be used to retrieve data from multiple tables in a single query, enabling us to draw data from multiple sources with one statement. Joins can be used to perform a variety of tasks, such as combining data from multiple tables, creating complex queries that span multiple tables, and combining multiple tables into one temporary table.

There are four main types of joins: inner join, left join, right join, and full outer join.

Inner join is the most commonly used join. It returns rows only when there is a match between two tables. An inner join combines all the rows from both tables that meet the join condition. For example, if we want to query the names of all the students in a school, we can use an inner join to combine the student and school tables.

Left join returns all the rows from the left table, even if there are no matches in the right table. It is used to return all the rows from the left table and the matching rows from the right table. For example, if we want to query the names of all the students in a school, and the name of their teachers, we can use a left join to combine the student and teacher tables.

Right join works in the same way as left join except it returns all the rows from the right table, even if there are no matches in the left table. It is used to return all the rows from the right table and the matching rows from the left table. For example, if we want to query the names of all the teachers and the names of their students, we can use a right join to combine the teacher and student tables.

Full outer join returns all the rows from both tables, regardless of whether there are matches or not. It is used to return all the rows from both tables, regardless of whether there are matches or not. For example, if we want to query the names of all the students and the names of their teachers, we can use a full outer join to combine the student and teacher tables.

SQL joins are an essential part of any database query language. They provide a powerful and flexible way to combine data from multiple tables into one result set. By understanding the different types of joins and their uses, we can create complex queries that span multiple tables and combine multiple tables into one temporary table.