Database Reference
In-Depth Information
Figure 7.5
The Concatenation
(||) Operator.
7.2.5
Set Operators
The various set operators effectively allow the merging of results of two sep-
arate queries in the form of <query> operator <query> (more detail and
examples in Chapter 13).
UNION [ ALL ] retrieves all rows in both queries. The ALL modifier
includes all duplicates; otherwise only unique rows are retrieved.
INTERSECT returns the intersection of two queries, namely rows
common to both queries.
MINUS returns all unique rows in the first query but not in the sec-
ond query.
7.2.6
Multiset Operators
Where set operators do things with query results of two queries, multiset
operators perform a similar function between two nested tables. Require-
