Define the following terms and give one example of each.

Question

1. Equijoin
2. Outer join
3. Self-join
4. Minus
5. Cartesian product

Answer 1

1. Equijoin
An equijoin is perfomred on two tables with a common column. The rows in two tables
are joined based on same value in the common columns. For example, employee and dept
tables.
2. Outer join
An outer join is similar to equijoin, but it also returns rows that do not have matching
rows in the other table. Equijoin does not return rows without a match. For example,
employee and dependent tables.
3. Self-join
A self-join joins a table to itself. A table with two columns having related values can be
self-joined. For example, employee table (columns EmployeeId and Supervisor), and
course table (CourseId and PreReq columns).
4. Minus
Minus operation returns rows in the first table that do not appear in the second table.
5. Cartesian product
Cartesian product between two tables matches each row from a table with every ro in the second table unconditionally.