About
Set - Difference in Relational Operator
set-difference is a relational operator that takes all Tuples in the relation 1, but not in relation 2
It's also known as:
- except,
- or minus
It returns all tuples (row) appearing in the first, but not the second of two union-compatible (ie same column, same type) relations.
Articles Related
Syntax
<MATH> R_1 - R_2 </MATH>
Duplicate
By default, it will remove all Tuples from the relation 1 even if it contains duplicate.
Example
- Relation 1
| Relation 1 |
|---|
| 1 |
| 1 |
| 2 |
- Relation 2
| Relation 2 |
|---|
| 1 |
| 2 |
- Except
"Relation 1" EXCEPT "Relation 2"
// empty