Database Reference
In-Depth Information
Figure 7.4
The NOT Logical
Operator.
7.2.3
The Concatenation Operator
The concatenation operator (||) allows concatenation of strings. The exam-
ple following concatenates two strings from two separate tables in an SQL
join (see Chapter 10). The result is shown in Figure 7.5.
SELECT NAME||' WROTE '||TITLE
FROM ARTIST NATURAL JOIN SONG
WHERE TITLE LIKE '%A%';
7.2.4
Hierarchical Query Operators
There are two hierarchical query operators, which are discusssed in more
detail with examples in Chapter 13.
PRIOR is used with the CONNECT BY condition evaluating the
subsequent expression for each parent row of each current row, using
a current row column to hook into a parent row column.
CONNECT_BY_ROOT performs a similar function to that
of CONNECT BY PRIOR except using the root row of the hierar-
chy as opposed to the parent row.
