Oracle SQL Queries Asked In Fiserv Written Test Interview

Oracle SQL query that shows Oracle users connected and the sessions number for user

SELECT username Usuario_Oracle, COUNT (username) Numero_Sesiones
    FROM v$session
GROUP BY username
ORDER BY Numero_Sesiones DESC;

Get number of objects per owner

SELECT owner, COUNT (owner) number_of_objects
    FROM dba_objects
GROUP BY owner
ORDER BY number_of_objects DESC;

Convert number to words

More info: Converting number into words in Oracle

SELECT TO_CHAR (TO_DATE (1526, 'j'), 'jsp') FROM DUAL;
Output:

one thousand five hundred twenty-six

Find string in package source code

Below query will search for string ‘FOO_SOMETHING’ in all package source. This query comes handy when you want to find a particular procedure or function call from all the source code.

--search a string foo_something in package source code
SELECT *
  FROM dba_source
 WHERE UPPER (text) LIKE '%FOO_SOMETHING%'
AND owner = 'USER_NAME';

Convert Comma Separated Values into Table

The query can come quite handy when you have comma separated data string that you need to convert into table so that you can use other SQL queries like IN or NOT IN. Here we are converting ‘AA,BB,CC,DD,EE,FF’ string to table containing AA, BB, CC etc. as each row. Once you have this table you can join it with other table to quickly do some useful stuffs.

WITH csv
     AS (SELECT 'AA,BB,CC,DD,EE,FF'
                   AS csvdata
           FROM DUAL)
    SELECT REGEXP_SUBSTR (csv.csvdata, '[^,]+', 1, LEVEL) pivot_char
      FROM DUAL, csv
CONNECT BY REGEXP_SUBSTR (csv.csvdata,'[^,]+', 1, LEVEL) IS NOT NULL;

Find the last record from a table

This ones straight forward. Use this when your table does not have primary key or you cannot be sure if record having max primary key is the latest one.

SELECT *
  FROM employees
 WHERE ROWID IN (SELECT MAX (ROWID) FROM employees);

(OR)

SELECT * FROM employees
MINUS
SELECT *
  FROM employees
 WHERE ROWNUM < (SELECT COUNT (*) FROM employees);

Oracle SQL Queries Most Frequently Asked In Fiserv Written Test Interview

Row Data Multiplication in Oracle

This query use some tricky math functions to multiply values from each row. Read below article for more details.
More info: Row Data Multiplication In Oracle

WITH tbl
     AS (SELECT -2 num FROM DUAL
         UNION
         SELECT -3 num FROM DUAL
         UNION
         SELECT -4 num FROM DUAL),
     sign_val
     AS (SELECT CASE MOD (COUNT (*), 2) WHEN 0 THEN 1 ELSE -1 END val
           FROM tbl
          WHERE num < 0)
  SELECT EXP (SUM (LN (ABS (num)))) * val
    FROM tbl, sign_val
GROUP BY val;

Generating Random Data In Oracle

You might want to generate some random data to quickly insert in table for testing. Below query help you do that. Read this article for more details.
More info: Random Data in Oracle

SELECT LEVEL empl_id,
           MOD (ROWNUM, 50000) dept_id,
           TRUNC (DBMS_RANDOM.VALUE (1000, 500000), 2) salary,
           DECODE (ROUND (DBMS_RANDOM.VALUE (1, 2)),  1, 'M',  2, 'F') gender,
           TO_DATE (
                 ROUND (DBMS_RANDOM.VALUE (1, 28))
              || '-'
              || ROUND (DBMS_RANDOM.VALUE (1, 12))
              || '-'
              || ROUND (DBMS_RANDOM.VALUE (1900, 2010)),
              'DD-MM-YYYY')
              dob,
           DBMS_RANDOM.STRING ('x', DBMS_RANDOM.VALUE (20, 50)) address
      FROM DUAL
CONNECT BY LEVEL < 10000;

Random number generator in Oracle

Plain old random number generator in Oracle. This ones generate a random number between 0 and 100. Change the multiplier to number that you want to set limit for.

--generate random number between 0 and 100
SELECT ROUND (DBMS_RANDOM.VALUE () * 100) + 1 AS random_num FROM DUAL;

Check if table contains any data

This one can be written in multiple ways. You can create count(*) on a table to know number of rows. But this query is more efficient given the fact that we are only interested in knowing if table has any data.

SELECT 1
  FROM TABLE_NAME
 WHERE ROWNUM = 1;

Oracle Select Query

Oracle select query is used to fetch records from database. For example:

SELECT * from customers;

Oracle Insert Query

Oracle insert query is used to insert records into table. For example:

insert into customers values(101,'rahul','delhi');

Oracle Update Query

Oracle update query is used to update records of a table. For example:

update customers set name='bob', city='london' where id=101;

Oracle Delete Query

Oracle update query is used to delete records of a table from database. For example:

delete from customers where id=101;

Get position of 'o' in name 'John' from employee table

Select instr(FIRST_NAME,'o') from employee where first_name = 'John'

Oracle Truncate Query

Oracle update query is used to truncate or remove records of a table. It doesn't remove structure. For example:

truncate table customers;

Get First_Name from employee table after replacing 'o' with '$'

select REPLACE(FIRST_NAME,'o','$') from employee

Oracle Drop Query

Oracle drop query is used to drop a table or view. It doesn't have structure and data. For example:

drop table customers;

Write a query to find the total sales of each product.?

Solution:

This is a simple query. You just need to group by the data on PRODUCT_NAME and then find the sum of sales.

SELECT P.PRODUCT_NAME,
       NVL( SUM( S.QUANTITY*S.PRICE ), 0) TOTAL_SALES
FROM   PRODUCTS P
       LEFT OUTER JOIN
       SALES S
ON     (P.PRODUCT_ID = S.PRODUCT_ID)
GROUP BY P.PRODUCT_NAME;

Write a query to find the products whose quantity sold in a year should be greater than the average quantity of the product sold across all the years?

Solution:

This can be solved with the help of correlated query. The SQL query for this is

SELECT P.PRODUCT_NAME,
       S.YEAR,
       S.QUANTITY
FROM   PRODUCTS P,
       SALES S
WHERE  P.PRODUCT_ID = S.PRODUCT_ID
AND    S.QUANTITY >
       (SELECT AVG(QUANTITY)
       FROM SALES S1
       WHERE S1.PRODUCT_ID = S.PRODUCT_ID
       );

Write a query to compare the products sales of "IPhone" and "Samsung" in each year? The output should look like as

YEAR IPHONE_QUANT SAM_QUANT IPHONE_PRICE SAM_PRICE
---------------------------------------------------
2010   10           20       9000         7000
2011   15           18       9000         7000
2012   20           20       9000         7000

Solution:

By using self-join SQL query we can get the required result. The required SQL query is

SELECT S_I.YEAR,
       S_I.QUANTITY IPHONE_QUANT,
       S_S.QUANTITY SAM_QUANT,
       S_I.PRICE    IPHONE_PRICE,
       S_S.PRICE    SAM_PRICE
FROM   PRODUCTS P_I,
       SALES S_I,
       PRODUCTS P_S,
       SALES S_S
WHERE  P_I.PRODUCT_ID = S_I.PRODUCT_ID
AND    P_S.PRODUCT_ID = S_S.PRODUCT_ID
AND    P_I.PRODUCT_NAME = 'IPhone'
AND    P_S.PRODUCT_NAME = 'Samsung'
AND    S_I.YEAR = S_S.YEAR

Write a query to find the ratios of the sales of a product?

Solution:

The ratio of a product is calculated as the total sales price in a particular year divide by the total sales price across all years. Oracle provides RATIO_TO_REPORT analytical function for finding the ratios. The SQL query is

SELECT P.PRODUCT_NAME,
       S.YEAR,
       RATIO_TO_REPORT(S.QUANTITY*S.PRICE)
         OVER(PARTITION BY P.PRODUCT_NAME ) SALES_RATIO
FROM   PRODUCTS P,
       SALES S
WHERE (P.PRODUCT_ID = S.PRODUCT_ID);

In the SALES table quantity of each product is stored in rows for every year. Now write a query to transpose the quantity for each product and display it in columns? The output should look like as

PRODUCT_NAME QUAN_2010 QUAN_2011 QUAN_2012
------------------------------------------
IPhone       10        15        20
Samsung      20        18        20
Nokia        25        16        8

Solution:

Oracle 11g provides a pivot function to transpose the row data into column data. The SQL query for this is

SELECT * FROM
(
SELECT P.PRODUCT_NAME,
       S.QUANTITY,
       S.YEAR
FROM   PRODUCTS P,
       SALES S
WHERE (P.PRODUCT_ID = S.PRODUCT_ID)
)A
PIVOT ( MAX(QUANTITY) AS QUAN FOR (YEAR) IN (2010,2011,2012));

If you are not running oracle 11g database, then use the below query for transposing the row data into column data.

SELECT P.PRODUCT_NAME,
       MAX(DECODE(S.YEAR,2010, S.QUANTITY)) QUAN_2010,
       MAX(DECODE(S.YEAR,2011, S.QUANTITY)) QUAN_2011,
       MAX(DECODE(S.YEAR,2012, S.QUANTITY)) QUAN_2012
FROM   PRODUCTS P,
       SALES S
WHERE (P.PRODUCT_ID = S.PRODUCT_ID)
GROUP BY P.PRODUCT_NAME;

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