Operations on Union, intersection, and difference sets in Oracle

1. union calculation selectnamefromtest1union [all] selectnamefromtest2; when union is used, results are sorted by default, while unionall is not

1. The union operation select name from test1 union [all] select name from test2; when union is used, results are sorted by default, and union all is not

1. Union Operation

Select name from test1

Union [all]

Select name from test2;

When union is used, results are sorted by default, and union all is not sorted, which consumes less resources. However, union all does not perform deduplication ~

2. intersection calculation

Select name from test1

Intersect

Select name from test2;

Oracle does not support the Intersect all keyword!

3. Difference Calculation

Select name from test1

Minus

Select name from test2;

The difference calculation in Oracle is different from the SQL standard. In the SQL standard, we use the following functions for the difference calculation.

Select name from test1

Counter T [all]

Select name from test2;