Why Joins are required The information needed to satisfy a user query requires more than one table. For example, the EMPLOYEES table has a column with a department number but not a department name; the department name must be retrieved from the DEPARTMENTS table. You can get this information by joining the two tables on a common column, in this case, the DEPARTMENT_ID column. Two or more tables can also be joined in situations where the columns may not be equal. Type of Joins 1) Equijoin or Inner Join or Natural Join 2) Outer Joins a) Left Outer Join b) Right Outer Join c) Full Outer Join 3) Self-Joins Equijoi...