A Join is a query that combines data from two or more tables into a single result set. The most common type of join is an inner join, which returns only the rows that match in both tables. An outer join returns all the rows from one table, plus any matching rows from the other table (or tables). There are several other types of joins as well, including left joins, right joins, and full outer joins.Joins are typically used to retrieve data from multiple tables where there is a relationship between the data in the tables. For example, you might use a join to retrieve customer information and order information for those customers. The customer information would be stored in one table, and the order information would be stored in another table. By using a join, you can combine the data from both tables into a single result set.PostgreSQL offers a variety of different join types that can be used to retrieve data from multiple tables. The most common join type is the inner join, which returns all rows from both tables that match the specified condition. Other join types include the left outer join, right outer join, and full outer join. PostgreSQL also supports a special type of join called a self-join, which is used to compare rows within a single table.A join is a clause in SQL that allows two tables to be related to each other. When two tables are joined, the data in the matching columns in the two tables is combined into a single row. The most common type of join is an inner join, which returns only rows that have matching values in both tables.A join is a query that combines data from two or more tables. The most common type of join is an inner join, which returns only the rows that match in both tables. To specify an inner join in SQL, you use the INNER JOIN keyword. For example:SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;This query would return all the rows from table1 and table2 where the id column in both tables match.