Reverse a number in PL/SQL

Prerequisite - PL/SQL introduction In PL/SQL code groups of commands are arranged within a block. A block group related declarations or statements. In declare part, we declare variables and between begin and end part, we perform the operations. Explanation: Consider the example, input = 12345. Step 1 : mod(12345,10) = 5 rev:= 0*10 + 5 = 5 num = floor(12345/10) = 1234 Step 2 : mod(1234,10) = 4 rev:= 5*10 + 4 = 54 num = floor(1234/10) = 123 Step 3 : mod(123,10) = 3 rev:= 54*10 + 3 = 543 num = floor(123/10) = 12 Step 4 : mod(12,10) = 2 rev:= 543*10 + 2 = 5432 num = floor(12/10) = 1 Step 5 : mod(1,10) = 1 rev:= 5432*10 + 1 = 54321 num = floor(1/10) = 0 in step 5, num =0 which doesn't satisfy the while condition and loop terminates. rev = 54321 More examples:

Input : 123456
Output :654321

Input :87459
Output :95478

Below is the required implementation: SQL

SET SERVEROUTPUT ON;
DECLARE
-- declare a number 'num' for reading actual input
-- declare another number 'rev' that would be reverse of num
num NUMBER;
rev NUMBER;

BEGIN
-- & is used to read input from keyboard
num:=#
-- initialize rev to 0
rev:=0;
-- the loop runs until num is greater than 0
WHILE num>0 LOOP
-- mod function is used to find the modulus/ remainder of num when divided by 10

rev:=(rev*10) + mod(num,10);
-- floor function is used to obtain a result which is an integer
num:=floor(num/10);
END LOOP;
DBMS_OUTPUT.PUT_LINE('Reverse of the number is: ' || rev);
END;
/                        

-- Program End

Output:

Enter value for num : 157439
Reverse of the number is: 934751