Review on Overview of Oracle Operators
Husandeep Kaur · International Journal for Research in Applied Science and Engineering Technology · 2017
SQL set operators allows combine results from two or more SELECT statements. At first sight this looks similar to SQL joins although there is big difference. SQL joins tends to combine columns i.e. with each additionally joined table it is possible to select more and more columns. You can combine multiple queries using the set operators UNION, UNION ALL, INTERSECT, and MINUS. All set operators have equal precedence. If a SQL statement contains multiple set operators, Oracle evaluates them from the left to right if no parentheses explicitly specify another order.