What is << some text >> in oracle - sql

Question

I found this character while reading some blog of pl sql << some text >> .
I found this character from following blog http://www.oracle-base.com/articles/8i/collections-8i.php

Answer 1

As others have said, <<some_text>> is a label named "some_text". Labels aren't often used in PL/SQL but can be helpful in a variety of contexts.
As an example, let's say you have several nested loops, execution has reached the very inner-most level, and the code needs to exit from all the nested loops and continue after the outer-most one. Here a label can be used in the following fashion:
<<outer_most_loop>>
LOOP
...
<<next_inner_loop>>
LOOP
...
<<inner_most_loop>>
LOOP
...
IF something <> something_else THEN
EXIT outer_most_loop;
END IF;
...
END LOOP inner_most_loop;
...
END LOOP next_inner_loop;
...
END LOOP outer_most_loop;
-- Execution continues here after EXIT outer_most_loop;
something := something_else;
...
Next, let's say that you've got some code with nested blocks, each of which declares a variable of the same name, so that you need to instruct the compiler about which of the same-named variables you intend to use. In this case you could use a label like this:
<<outer>>
DECLARE
nNumber NUMBER := 1;
BEGIN
<<inner>>
DECLARE
nNumber NUMBER := 2;
BEGIN
DBMS_OUTPUT.PUT_LINE('outer.nNumber=' || outer.nNumber);
DBMS_OUTPUT.PUT_LINE('inner.nNumber=' || inner.nNumber);
END inner;
END outer;
Labels can also be useful if you insist on giving a variable the same name as a column in a table. As an example, let's say that you have a table named PEOPLE with a non-nullable column named LASTNAME and you want to delete everyone with LASTNAME = 'JARVIS'. The following code:
DECLARE
lastname VARCHAR2(100) := 'JARVIS';
BEGIN
DELETE FROM PEOPLE
WHERE LASTNAME = lastname;
END;
will not do what you intended - instead, it will delete every row in the PEOPLE table. This occurs because in the case of potentially ambiguous names, PL/SQL will choose to use the column in the table instead of the local variable or parameter; thus, the above is interpreted as
DECLARE
lastname VARCHAR2(100) := 'JARVIS';
BEGIN
DELETE FROM PEOPLE p
WHERE p.LASTNAME = p.lastname;
END;
and boom! Every row in the table goes bye-bye. :-) A label can be used to qualify the variable name as follows:
<<outer>>
DECLARE
lastname VARCHAR2(100) := 'JARVIS';
BEGIN
DELETE FROM PEOPLE p
WHERE p.LASTNAME = outer.lastname;
END;
Execute this and only those people with LASTNAME = 'JARVIS' will vanish.
And yes - as someone else said, you can GOTO a label:
FUNCTION SOME_FUNC RETURN NUMBER
IS
SOMETHING NUMBER := 1;
SOMETHING_ELSE NUMBER := 42;
BEGIN
IF SOMETHING <> SOMETHING_ELSE THEN
GOTO HECK;
END IF;
RETURN 0;
<<HECK>>
RETURN -1;
END;
(Ewwwww! Code like that just feels so wrong..!)
Share and enjoy.

Answer 2

It's often used to label loops, cursors, etc.
You can use that label in goto statements. Else, it is just 'comment'.
Sample from Oracle:
DECLARE
p VARCHAR2(30);
n PLS_INTEGER := 37; -- test any integer > 2 for prime
BEGIN
FOR j in 2..ROUND(SQRT(n)) LOOP
IF n MOD j = 0 THEN -- test for prime
p := ' is not a prime number'; -- not a prime number
GOTO print_now; -- << here is the GOTO
END IF;
END LOOP;
p := ' is a prime number';
<<print_now>> -- << and it executes this
DBMS_OUTPUT.PUT_LINE(TO_CHAR(n) || p);
END;
/

Answer 3

It is a label, a subgroup of comments in the plsql syntax.
http://ss64.com/oraplsql/operators.html

Answer 4

Its is a label delimeter
<< label delimiter (begin)
label delimiter (end) >>
http://docs.oracle.com/cd/B10501_01/appdev.920/a96624/02_funds.htm