Interview Questions and Answers for 'Sql' | Search Interview Question

Interview Questions and Answers - Order By Rating

Q31. Difference between relational databases and NoSQL databases ?

Database

Ans. https://www.mongodb.com/scale/nosql-vs-relational-databases

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database management nosql database relational database Asked in 1 Companies frequent}

Q32. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?

Database

Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.

Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql joins self join self-join Pair of employee names with first having lesser salary than later Pair of department names where first dept has lesser employees than the later Asked in 26 Companies basic frequent}

Q33. What is the use of Transient Keyword ?

Core Java

Ans. It in Java is used to indicate that a field should not be serialized.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops serialization transient java keywords Asked in 39 Companies intermediate frequent}

Try 2 Question(s) Test

Q34. Difference between Inner and Outer Join ?

Database

Ans. Inner join is the intersection of two tables on a particular columns whereas Outer Join is the Union of two tables.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql joins inner join outer join Asked in 4 Companies basic frequent}

Q35. What is a Cursor ?

Database

Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve databases sql cursors packages Asked in 5 Companies basic frequent}

Q36. What are temp tables ?

Ans. These are the tables that are created temporarily and are deleted once the Stored Procedure is complete.

For example - we may like to pull some info from a table and then do some operations on that data and then store the output in final output table. We can store the intermediary values in a temp table and once we have final output with us, we can just delete it.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database sql temp tables tables}

Q37. Does SQL allow null values ? Can we use it within Where clause ?

Ans. Yes , we can have null values for columns in SQL. Null value represent that the columns value is unknown or haven't been filled. Yes, We can use it within where clause to get the rows with null values.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql sql null values sql where clause databases}

Q38. Write an SQL to find all records having all upper case alphanumeric characters in a field ?

Ans. Select * from Table where field = upper(field)

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database}

Q39. Write an SQL to find all records having all numeric characters in a field ?

Ans. Select * from Table where isnumeric(field) = 1;

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database}

Q40. Do you know of any DB statement that can be used if we would like to insert multiple rows into a table ?

Database

Ans. We can use INSERT ALL.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database insert dml statement sql}

Q41. What things you will look for if you get following exception while making DB call ?

table or view does not exist

Database

Ans. First will check if the table or view actually exist in the DB

If it does , Will make sure to see that the application has rights on the schema that holds the respective Table.

Will then make sure that we have prefixed the schema with the table name while accessing it.

Will then make sure that its not DB Cache that's causing it as the table DDL might have been created recently.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle technical lead}

Q42. What's the benefit for specifying constraints like Not Null , Primary Key explicitly instead of specifying it against the column ?

Database

Ans. In case we specify them explicitly we can have control over constraint name as otherwise they will be system generated. It provides an ease in case we plan to drop the constraint in future.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q43. How can we disable a constraint ?

Database

Ans. alter table
table_name
DISABLE constraint
constraint_name;

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q44. Can we have foreign key reference to a non primary key column ?

Database

Ans. Yes, but the respective key in the foreign table should be declared Unique.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle Asked in 2 Companies}

Q45. What should be done for auto generating primary key id in a table ?

Database

Ans. We need to create a sequence.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q46. Which constraint cannot be specified as an explicit constraint and should be specified with the column only ?

Database

Ans. NOT NULL

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql oracle database ddl constraint table creation}

Q47. How to know the structure of a Table in Oracle ?

Database

Ans. DESC

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q48. How to know the constraints on a Table in Oracle ?

Database

Ans. SELECT *
FROM user_constraints
WHERE table_name = ''

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q49. How to know the default column value of a Table in Oracle ?

Database

Ans. Select DATA_DEFAULT
from DBA_TAB_COLUMNS
where TABLE_NAME = '' and COLUMN_NAME='';

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sql database oracle}

Q50. In majority of the cases, the following join will give maximum number of results ? Reference

Database

a. Inner Join

b. Outer Join

c. Left Join

d. Right Join

Ans.b. Outer Join

Q51. Which if the following is true for SQL Joins ? Reference

Database

a. Left Join and Right Join gives equal number of Results

b. Outer Join and Inner Join gives equal number of Results

c. Inner Join gives maximum number of results records

d. Inner Join gives minimum number of result records

Ans.d. Inner Join gives minimum number of result records

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.