control statement PL/SQL

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TO COMMENT A CODE
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(--) ---->Single line comment
(/* */)-->Multiple line comment
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IF STATEMENT
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/*GREATEST AMONG THREE (USE OF IF)*/
DECLARE
A NUMBER(2):=&A;
B NUMBER(2):=&B;
C NUMBER(2):=&C;
BEGIN
IF A>B AND A>C THEN
DBMS_OUTPUT.PUT_LINE(A||'IS LARGEST');
ELSIF B>A AND B>C THEN
DBMS_OUTPUT.PUT_LINE(B||'IS LARGEST');
ELSE
DBMS_OUTPUT.PUT_LINE(C||'IS LARGEST');
END IF;
END;
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Looping using EXIT WHEN statement
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declare
counter number(2):=0;
begin
loop
DBMS_OUTPUT.PUT_LINE('the count is'||counter);
counter:=counter+1;
exit when counter=10;
end loop;
end;
/

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****************************
Looping using WHILE
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declare
counter number(2):=0;
begin
WHILE COUNTER<=10
loop
DBMS_OUTPUT.PUT_LINE('the count is'||counter);
counter:=counter+1;
end loop;
end;
/
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****************************
Looping using WHILE BUT
NOT INITIALIZING THE COUNTER
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declare
counter1 number(2);
begin
WHILE COUNTER1<=10
loop
DBMS_OUTPUT.PUT_LINE('the SECOND count is'||counter1);
counter1:=counter1+1;
end loop;
end;
/
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****************************
Looping using FOR INCREMENT SINGLE
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declare
counter1 number(2);
begin
FOR COUNTER1 IN 1..10
loop
DBMS_OUTPUT.PUT_LINE('the count is'||counter1);
end loop;
end;
/

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****************************
LOOPING USING GOTO
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DECLARE
A NUMBER(2):=0;
BEGIN
LOOP
DBMS_OUTPUT.PUT_LINE(A);
A:=A+1;
IF A>10 THEN
GOTO END_OF_LOOP;
END IF;
END LOOP;
<>
DBMS_OUTPUT.PUT_LINE('THE LOOP IS END');
LOOP
A:=A-1;
DBMS_OUTPUT.PUT_LINE(A);
EXIT WHEN A<=5;
END LOOP;
END;
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****************************
Using NULL as a statement
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DECLARE
v NUMBER := 7;
BEGIN
IF v<5 THEN
dbms_output.put_line('less than 7');
ELSIF v>7 THEN
dbms_output.put_line('Greater than 7');
ELSE
NULL; -- Do nothing
END IF;
END;
/