Some Interesting Sql Queries

Some Interesting SQL Queries, www.askhareesh.com
Query to retrieve 1,4,7,10.....rows from a table

SELECT a.* FROM emp a WHERE (ROWID, 1) IN (SELECT ROWID, MOD (ROWNUM, 3) FROM emp);

Query to print Rupees in words 

SELECT sal "Salary ", (' Rs. ' (TO_CHAR (TO_DATE (sal, 'j'), 'Jsp')) ' only.' ) "Sal in Words" FROM emp

Query to print the calender for the year

SELECT LPAD (MONTH, 20 - (20 - LENGTH (MONTH)) / 2) MONTH, "Sun", "Mon",
"Tue", "Wed", "Thu", "Fri", "Sat"
FROM (SELECT TO_CHAR (dt, 'fmMonthfm YYYY') MONTH,
TO_CHAR (dt + 1, 'iw') week,
MAX (DECODE (TO_CHAR (dt, 'd'),
'1', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Sun",
MAX (DECODE (TO_CHAR (dt, 'd'),
'2', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Mon",
MAX (DECODE (TO_CHAR (dt, 'd'),
'3', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Tue",
MAX (DECODE (TO_CHAR (dt, 'd'),
'4', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Wed",
MAX (DECODE (TO_CHAR (dt, 'd'),
'5', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Thu",
MAX (DECODE (TO_CHAR (dt, 'd'),
'6', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Fri",
MAX (DECODE (TO_CHAR (dt, 'd'),
'7', LPAD (TO_CHAR (dt, 'fmdd'), 2)
)
) "Sat"
FROM (SELECT TRUNC (SYSDATE, 'y') - 1 + ROWNUM dt
FROM all_objects
WHERE ROWNUM <= ADD_MONTHS (TRUNC (SYSDATE, 'y'), 12) - TRUNC (SYSDATE, 'y')) GROUP BY TO_CHAR (dt, 'fmMonthfm YYYY'), TO_CHAR (dt + 1, 'iw'))
ORDER BY TO_DATE (MONTH, 'Month YYYY'), TO_NUMBER (week)

Use of Order by clause for records with datatype as character

We generally cannot order the records for a column with character data type. Please use the following trick to use the order clause:

select employee_number from employees
order by lpad(employee_number,100);

Using the lpad the zeros would be appended and then sql will treat them as numbers and the employee number would be sorted.

Printing Fibonacci series in PL/SQL

DECLARE
RESULT NUMBER := 1;
previous NUMBER := -1;
l_sum NUMBER;
n NUMBER;
l_in NUMBER := 10;
BEGIN
FOR n IN 1 .. l_in
LOOP
l_sum := RESULT + previous;
previous := RESULT;
RESULT := l_sum;
DBMS_OUTPUT.put_line (l_sum);
END LOOP;
END;

Other ways to print the Fib series is as follows:

CREATE OR REPLACE FUNCTION fib (n POSITIVE) RETURN INTEGER IS
BEGIN
IF (n = 1) OR (n = 2) THEN -- terminating condition
RETURN 1;
ELSE
RETURN fib(n - 1) + fib(n - 2); -- recursive call
END IF;
END fib;

/

-- Test Fibonacci Series:
SELECT fib(1), fib(2), fib(3), fib(4), fib(5) FROM dual;


Demonstrate simple encoding and decoding of secret messages 

SELECT TRANSLATE(
'HELLO WORLD', -- Message to encode
'ABCDEFGHIJKLMNOPQRSTUVWXYZ ',
'1234567890!@#$%^&*()-=_+;,.') ENCODED_MESSAGE
FROM DUAL
/

SELECT TRANSLATE(
'85@@%._%*@4', -- Message to decode
'1234567890!@#$%^&*()-=_+;,.',
'ABCDEFGHIJKLMNOPQRSTUVWXYZ ') DECODED_MESSAGE
FROM DUAL
/



*/