TB_BGT_INFO.BGT_ID = TB_QUOTA_INFO.BGT_ID(+) means left join
-------------------------
SELECT ename , dname
FROM Emp, Dept
WHERE Emp.Deptno(+) = Dept.Deptno
can also be written as:
SELECT ename , dname
FROM Emp RIGHT JOIN Dept
ON Emp.Deptno = Dept.Deptno
This SQL text uses a right join, that is, " (+)" is the direction of the connection. The right connection indicates that all records on the right side of the equal sign will be displayed, regardless of whether they are matched on the left side, that is to say, in the above example, whether they appear or not If a department does not have an employee, the name of the department will appear in the query results.