Virtusa Oracle SQL Queries In Written Test Interview

Virtusa Frequently Asked Oracle SQL Queries In Written Test Interview Questions

Write a query to display each letter of the word "BIG" in a separate row?

B
I
G

Solution:

SELECT SUBSTR('SMILE',LEVEL,1) A
FROM   DUAL
CONNECT BY LEVEL <=LENGTH('BIG');

Convert the string "SMILE" to Ascii values?  The output should look like as 83,77,73,76,69. Where 83 is the ascii value of S and so on.

The ASCII function will give ascii value for only one character. If you pass a string to the ascii function, it will give the ascii value of first letter in the string. Here i am providing two solutions to get the ascii values of string.

Solution 1:

SELECT SUBSTR(DUMP('SMILE'),15)
FROM DUAL;

Solution2:

SELECT WM_CONCAT(A)
FROM
(
SELECT ASCII(SUBSTR('SMILE',LEVEL,1)) A
FROM   DUAL
CONNECT BY LEVEL <=LENGTH('SMILE')
);

Virtusa Frequently Asked Oracle SQL Queries In Written Test Interview Questions

Consider the following friends table as the source

Name, Friend_Name

-----------------

sam,   ram

sam,   vamsi

vamsi, ram

vamsi, jhon

ram,   vijay

ram,   anand

Here ram and vamsi are friends of sam; ram and jhon are friends of vamsi and so on. Now write a query to find friends of friends of sam. For sam; ram,jhon,vijay and anand are friends of friends. The output should look as

Name, Friend_of_Firend

----------------------

sam,    ram

sam,    jhon

sam,    vijay

sam,    anand

Solution:

SELECT  f1.name,

        f2.friend_name as friend_of_friend

FROM    friends f1,

        friends f2

WHERE   f1.name = 'sam'

AND     f1.friend_name = f2.name;

This is an extension to the problem 1. In the output, you can see ram is displayed as friends of friends. This is because, ram is mutual friend of sam and vamsi. Now extend the above query to exclude mutual friends. The output should look as

Name, Friend_of_Friend

----------------------

sam,    jhon

sam,    vijay

sam,    anand

Solution:

SELECT  f1.name,

        f2.friend_name as friend_of_friend

FROM    friends f1,

        friends f2

WHERE   f1.name = 'sam'

AND     f1.friend_name = f2.name

AND     NOT EXISTS 

        (SELECT 1 FROM friends f3 

         WHERE f3.name = f1.name 

         AND   f3.friend_name = f2.friend_name);

Write a query to get the top 5 products based on the quantity sold without using the row_number analytical function? The source data looks as

Products, quantity_sold, year

-----------------------------

A,         200,          2009

B,         155,          2009

C,         455,          2009

D,         620,          2009

E,         135,          2009

F,         390,          2009

G,         999,          2010

H,         810,          2010

I,         910,          2010

J,         109,          2010

L,         260,          2010

M,         580,          2010

Solution:

SELECT  products,

        quantity_sold,

        year

FROM

(

  SELECT  products,

          quantity_sold, 

          year,

          rownum r

  from    t

  ORDER BY quantity_sold DESC

)A

WHERE r <= 5;

Write a query to produce the same output using row_number analytical function?

Solution:

SELECT  products,

        quantity_sold,

        year

FROM

(

  SELECT products,

         quantity_sold,

         year,

         row_number() OVER(

            ORDER BY quantity_sold DESC) r

  from   t

)A

WHERE r <= 5;

write a query to get the top 5 products in each year based on the quantity sold?

Solution:

SELECT  products,

        quantity_sold,

        year

FROM

(

   SELECT products,

          quantity_sold,

          year,

          row_number() OVER(

               PARTITION BY year 

               ORDER BY quantity_sold DESC) r

   from   t

)A

WHERE r <= 5;

Load the below products table into the target table.

CREATE TABLE PRODUCTS

(

       PRODUCT_ID     INTEGER,

       PRODUCT_NAME   VARCHAR2(30)

);

INSERT INTO PRODUCTS VALUES ( 100, 'Nokia');

INSERT INTO PRODUCTS VALUES ( 200, 'IPhone');

INSERT INTO PRODUCTS VALUES ( 300, 'Samsung');

INSERT INTO PRODUCTS VALUES ( 400, 'LG');

INSERT INTO PRODUCTS VALUES ( 500, 'BlackBerry');

INSERT INTO PRODUCTS VALUES ( 600, 'Motorola');

COMMIT;

SELECT * FROM PRODUCTS;

PRODUCT_ID PRODUCT_NAME

-----------------------

100        Nokia

200        IPhone

300        Samsung

400        LG

500        BlackBerry

600        Motorola

The requirements for loading the target table are:

Select only 2 products randomly.

Do not select the products which are already loaded in the target table with in the last 30 days.

Target table should always contain the products loaded in 30 days. It should not contain the products which are loaded prior to 30 days.

Solution:

First we will create a target table. The target table will have an additional column INSERT_DATE to know when a product is loaded into the target table. The target 

table structure is

CREATE TABLE TGT_PRODUCTS

(

       PRODUCT_ID     INTEGER,

       PRODUCT_NAME   VARCHAR2(30),

       INSERT_DATE    DATE

);

The next step is to pick 5 products randomly and then load into target table. While selecting check whether the products are there in the 

INSERT INTO TGT_PRODUCTS

SELECT  PRODUCT_ID,

        PRODUCT_NAME,

        SYSDATE INSERT_DATE

FROM

(

SELECT  PRODUCT_ID,

 PRODUCT_NAME

FROM PRODUCTS S

WHERE   NOT EXISTS (

           SELECT 1

           FROM   TGT_PRODUCTS T

           WHERE  T.PRODUCT_ID = S.PRODUCT_ID

        )

ORDER BY DBMS_RANDOM.VALUE --Random number generator in oracle.

)A

WHERE ROWNUM <= 2;

The last step is to delete the products from the table which are loaded 30 days back. 

DELETE FROM TGT_PRODUCTS

WHERE  INSERT_DATE < SYSDATE - 30;

Load the below CONTENTS table into the target table. 

CREATE TABLE CONTENTS

(

  CONTENT_ID  INTEGER,

  CONTENT_TYPE VARCHAR2(30)

);

INSERT INTO CONTENTS VALUES (1,'MOVIE');

INSERT INTO CONTENTS VALUES (2,'MOVIE');

INSERT INTO CONTENTS VALUES (3,'AUDIO');

INSERT INTO CONTENTS VALUES (4,'AUDIO');

INSERT INTO CONTENTS VALUES (5,'MAGAZINE');

INSERT INTO CONTENTS VALUES (6,'MAGAZINE');

COMMIT;

SELECT * FROM CONTENTS;

CONTENT_ID CONTENT_TYPE

-----------------------

1          MOVIE

2          MOVIE

3          AUDIO

4          AUDIO

5          MAGAZINE

6          MAGAZINE

The requirements to load the target table are: 

Load only one content type at a time into the target table.

The target table should always contain only one contain type.

The loading of content types should follow round-robin style. First MOVIE, second AUDIO, Third MAGAZINE and again fourth Movie.

Solution: 

First we will create a lookup table where we mention the priorities for the content types. The lookup table “Create Statement” and data is shown below. 

CREATE TABLE CONTENTS_LKP

(

  CONTENT_TYPE VARCHAR2(30),

  PRIORITY     INTEGER,

  LOAD_FLAG  INTEGER

);

INSERT INTO CONTENTS_LKP VALUES('MOVIE',1,1);

INSERT INTO CONTENTS_LKP VALUES('AUDIO',2,0);

INSERT INTO CONTENTS_LKP VALUES('MAGAZINE',3,0);

COMMIT;

SELECT * FROM CONTENTS_LKP;

CONTENT_TYPE PRIORITY LOAD_FLAG

---------------------------------

MOVIE         1          1

AUDIO         2          0

MAGAZINE      3          0

Here if LOAD_FLAG is 1, then it indicates which content type needs to be loaded into the target table. Only one content type will have LOAD_FLAG as 1. The other content types will have LOAD_FLAG as 0. The target table structure is same as the source table structure. 

The second step is to truncate the target table before loading the data 

TRUNCATE TABLE TGT_CONTENTS;

The third step is to choose the appropriate content type from the lookup table to load the source data into the target table. 

INSERT INTO TGT_CONTENTS

SELECT  CONTENT_ID,

 CONTENT_TYPE 

FROM CONTENTS

WHERE CONTENT_TYPE = (SELECT CONTENT_TYPE FROM CONTENTS_LKP WHERE LOAD_FLAG=1);

The last step is to update the LOAD_FLAG of the Lookup table. 

UPDATE CONTENTS_LKP

SET LOAD_FLAG = 0

WHERE LOAD_FLAG = 1;

UPDATE CONTENTS_LKP

SET LOAD_FLAG = 1

WHERE PRIORITY = (

SELECT DECODE( PRIORITY,(SELECT MAX(PRIORITY) FROM CONTENTS_LKP) ,1 , PRIORITY+1)

FROM   CONTENTS_LKP

WHERE  CONTENT_TYPE = (SELECT DISTINCT CONTENT_TYPE FROM TGT_CONTENTS)

);

Get Joining Date,Time including milliseconds from employee table

select to_char(JOINING_DATE,'dd/mm/yyyy HH:mi:ss.ff') from
EMPLOYEE . Column Data Type should be “TimeStamp”

Oracle Create Query

Oracle create query is used to create a table, view, sequence, procedure and function. For example:

CREATE TABLE customers
( id number(10) NOT NULL,
  name varchar2(50) NOT NULL,
  city varchar2(50),
CONSTRAINT customers_pk PRIMARY KEY (id) 
);

Oracle Alter Query

Oracle alter query is used to add, modify, delete or drop colums of a table. Let's see a query to add column in customers table:

ALTER TABLE customers
ADD age varchar2(50);