Oracle left and right connections

The left and right connections in oracle saves the complex join statements (left join and right join) in SQL server, which are represented by a "(+. In the following experiment, query 1 and query 2 are equivalent, and query 3 and query 4 are equivalent. Query 1: select first_name, department_name, emp. department_id from emp, parameters deptwhere emp. department_id (+) = dept. department_id; 122 rows selected. query 2: select first_name, department_name, emp. department_id from orders ments dept left join empon emp. department_id = dept. department_id; 122 rows selected. query 3: select first_name, department_name, emp. department_id from emp, parameters deptwhere emp. department_id = d Ept. department_id (+); 107 rows selected. query 4: select first_name, department_name, emp. department_id from emp left join orders ments Deton emp. department_id = dept. department_id; 107 rows selected. conclusion: 1. If (+) is on the other side, all records on the other side are returned. 2. (+) is placed on one side that contains null values. It cannot be used on both sides at the same time.