Hexaware Technologies Frequently Asked Oracle SQL Queries In Written Test Interview Questions
How to add column in a table
Syntax:
ALTER TABLE table_name
ADD column_name column-definition;
Example:
Consider that already existing table customers. Now, add a new column customer_age into the table customers.
ALTER TABLE customers
ADD customer_age varchar2(50);
Now, a new column "customer_age" will be added in customers table.
How to add multiple columns in the existing table
Syntax:
ALTER TABLE table_name
ADD (column_1 column-definition,
column_2 column-definition,
...
column_n column_definition);
Example
ALTER TABLE customers
ADD (customer_type varchar2(50),
customer_address varchar2(50));
Now, two columns customer_type and customer_address will be added in the table customers.
How to modify column of a table
Syntax:
ALTER TABLE table_name
MODIFY column_name column_type;
Example:
ALTER TABLE customers
MODIFY customer_name varchar2(100) not null;
Now the column column_name in the customers table is modified
to varchar2 (100) and forced the column to not allow null values.
How to modify multiple columns of a table
Syntax:
ALTER TABLE table_name
MODIFY (column_1 column_type,
column_2 column_type,
...
column_n column_type);
Example:
ALTER TABLE customers
MODIFY (customer_name varchar2(100) not null,
city varchar2(100));
This will modify both the customer_name and city columns in the table.
How to drop column of a table
Syntax:
ALTER TABLE table_name
DROP COLUMN column_name;
Example:
ALTER TABLE customers
DROP COLUMN customer_name;
This will drop the customer_name column from the table.
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;
Write a query to find the number of products sold in each year?
Solution:
To get this result we have to group by on year and the find the count. The SQL query for this question is
SELECT YEAR,
COUNT(1) NUM_PRODUCTS
FROM SALES
GROUP BY YEAR;
Write a query to generate sequence numbers from 1 to the specified number N?
Solution:
SELECT LEVEL FROM DUAL CONNECT BY LEVEL<=&N;
Write a query to display only Sunday dates from Jan, 2000 to till now?
Solution:
SELECT C_DATE,
TO_CHAR(C_DATE,'DY')
FROM
(
SELECT TO_DATE('01-JAN-2000','DD-MON-YYYY')+LEVEL-1 C_DATE
FROM DUAL
CONNECT BY LEVEL <=
(SYSDATE - TO_DATE('01-JAN-2000','DD-MON-YYYY')+1)
)
WHERE TO_CHAR(C_DATE,'DY') = 'SUN';
Write a query to duplicate each row based on the value in the repeat column? The input table data looks like as below
Products, Repeat
----------------
A, 3
B, 5
C, 2
Now in the output data, the product A should be repeated 3 times, B should be repeated 5 times and C should be repeated 2 times. The output will look like as below
Products, Repeat
----------------
A, 3
A, 3
A, 3
B, 5
B, 5
B, 5
B, 5
B, 5
C, 2
C, 2
Solution:
SELECT PRODUCTS,
REPEAT
FROM T,
( SELECT LEVEL L FROM DUAL
CONNECT BY LEVEL <= (SELECT MAX(REPEAT) FROM T)
) A
WHERE T.REPEAT >= A.L
ORDER BY T.PRODUCTS;
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')
);
How to add column in a table
Syntax:
ALTER TABLE table_name
ADD column_name column-definition;
Example:
Consider that already existing table customers. Now, add a new column customer_age into the table customers.
ALTER TABLE customers
ADD customer_age varchar2(50);
Now, a new column "customer_age" will be added in customers table.
How to add multiple columns in the existing table
Syntax:
ALTER TABLE table_name
ADD (column_1 column-definition,
column_2 column-definition,
...
column_n column_definition);
Example
ALTER TABLE customers
ADD (customer_type varchar2(50),
customer_address varchar2(50));
Now, two columns customer_type and customer_address will be added in the table customers.
 |
| Hexaware Technologies Frequently Asked Oracle SQL Queries In Written Test Interview Questions |
How to modify column of a table
Syntax:
ALTER TABLE table_name
MODIFY column_name column_type;
Example:
ALTER TABLE customers
MODIFY customer_name varchar2(100) not null;
Now the column column_name in the customers table is modified
to varchar2 (100) and forced the column to not allow null values.
How to modify multiple columns of a table
Syntax:
ALTER TABLE table_name
MODIFY (column_1 column_type,
column_2 column_type,
...
column_n column_type);
Example:
ALTER TABLE customers
MODIFY (customer_name varchar2(100) not null,
city varchar2(100));
This will modify both the customer_name and city columns in the table.
How to drop column of a table
Syntax:
ALTER TABLE table_name
DROP COLUMN column_name;
Example:
ALTER TABLE customers
DROP COLUMN customer_name;
This will drop the customer_name column from the table.
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;
Write a query to find the number of products sold in each year?
Solution:
To get this result we have to group by on year and the find the count. The SQL query for this question is
SELECT YEAR,
COUNT(1) NUM_PRODUCTS
FROM SALES
GROUP BY YEAR;
Write a query to generate sequence numbers from 1 to the specified number N?
Solution:
SELECT LEVEL FROM DUAL CONNECT BY LEVEL<=&N;
Write a query to display only Sunday dates from Jan, 2000 to till now?
Solution:
SELECT C_DATE,
TO_CHAR(C_DATE,'DY')
FROM
(
SELECT TO_DATE('01-JAN-2000','DD-MON-YYYY')+LEVEL-1 C_DATE
FROM DUAL
CONNECT BY LEVEL <=
(SYSDATE - TO_DATE('01-JAN-2000','DD-MON-YYYY')+1)
)
WHERE TO_CHAR(C_DATE,'DY') = 'SUN';
Write a query to duplicate each row based on the value in the repeat column? The input table data looks like as below
Products, Repeat
----------------
A, 3
B, 5
C, 2
Now in the output data, the product A should be repeated 3 times, B should be repeated 5 times and C should be repeated 2 times. The output will look like as below
Products, Repeat
----------------
A, 3
A, 3
A, 3
B, 5
B, 5
B, 5
B, 5
B, 5
C, 2
C, 2
Solution:
SELECT PRODUCTS,
REPEAT
FROM T,
( SELECT LEVEL L FROM DUAL
CONNECT BY LEVEL <= (SELECT MAX(REPEAT) FROM T)
) A
WHERE T.REPEAT >= A.L
ORDER BY T.PRODUCTS;
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')
);
Post a Comment