In SQL, what is a join?

In SQL, what is a join?

• An operation that combines columns from one or more tables
• An operation that connects two or more databases
• The same thing as a foreign key.
• The same thing as running a "Not-In"

EXPLANATION

An SQL join clause - corresponding to a join operation in relational algebra - combines columns from one or more tables in a relational database. It creates a set that can be saved as a table or used as it is. A JOIN is a means for combining columns from one (self-join) or more tables by using values common to each.

The SQL Joins clause is used to combine records from two or more tables in a database. A JOIN is a means for combining fields from two tables by using values common to each. ... LEFT JOIN − returns all rows from the left table, even if there are no matches in the right table.