SQL Interview Questions and Answers 2020

SQL Interview Questions

SQL Interview Questions and Answers 2020

BEST SQL INTERVIEW QUESTIONS AND ANSWERS 2020 | PREPARE FOR SQL INTERVIEW IN 2020 WITH THESE MOST ASKED REAL-WORLD SQL INTERVIEW QUESTIONS. SAVE TIME IN INTERVIEW PREPARATION.


1. Define SQL?

Ans: SQL stands for Structured Query Language. It is the language of the database. It is used to communicate with the database to insert, update, delete and view the data. It is used with a variety of databases like Oracle, SQL Server, MySQL, etc.


2. What are the advantages of using SQL?

Ans:

• Efficient

• Easy to learn and use

• Functionally complete (With SQL, you can define, retrieve, and manipulate data in the tables).


3. What are the capabilities of SQL?

Ans:

• Projection

• Selection

• Joining: You can use the join capability in SQL to bring together data that is stored in different tables by creating a link between them.


4. Define Projection?

Ans: Projection: You can use the projection capability in SQL to choose the columns in a table that you want your query to return. You can choose as few or as many columns of the table as you require.

SQL INTERVIEW QUESTIONS AND ANSWERS 2020
SQL INTERVIEW QUESTIONS AND ANSWERS 2020

5. Define Selection?

Ans: Selection: You can use the selection capability in SQL to choose the rows in a table that you want your query to return. You can use various criteria to restrict the rows that you see.


6. Write the syntax for the SELECT statement?

Ans

SELECT * | { [ DISTINCT] column | expression [alias],…}

FROM table;


7. How can you override precedence?

Ans: We can override precedence by using parenthesis.


8. Define Null?

Ans: A Null is a value that is unavailable, unassigned, unknown, or inapplicable.


9. Is Null equal to zero?

Ans: A Null is not the same as zero because zero is a number


10. Is Null equal to space?

Ans: A Null is not the same as a blank space because space is a character


11. What is the result of Null+3?

Ans: Null+3=Null


12. What will happen when you use Null value with any

Ans: If any value in an arithmetic expression is Null, the result is Null.

For e.g., if you attempt to perform division with zero, you get an error. However, if you divide a number by Null, the result is a Null or unknown.


13. Define column alias?

Ans: Column alias renames a column heading. It is the alternative name given to the column, as the column heading may not be descriptive and hence may be difficult to understand. So we use column alias to change the name of the column.


14. What is the use of column alias?

Ans: When displaying the result of a query, the name of the selected column is given a column heading. The column heading may not be descriptive and hence may be difficult to understand. So we use column alias to change the name of the column.


15. How are duplicate data eliminated from the table?

Ans: By using the DISTINCT keyword in the SELECT clause duplicate date gets eliminated.


16. Does the column alias change the column name in the table?

Ans: No, Column alias does not change the column name in the table. It changes the heading of the column in the query which is created for displaying data temporary only


17. How do you see the structure of a table?

Ans: Execute the DESCRIBE command to display the structure of a table.

DESC  table name or DESCRIBE  table name


18. What is the purpose of the WHERE clause?

Ans: Used to filter the data from the table by using conditions.


19. List the SQL operators according to their precedence?

Ans:

SQL INTERVIEW QUESTIONS AND ANSWERS 2020

20. What is the purpose of a LIKE operator?

Ans: It selects rows that match a character pattern. Two wildcards are used in like operator

% (Percentage Sign): It denotes zero or more characters

_ (Underscore Character): It denotes exactly one character


SQL INTERVIEW QUESTIONS AND ANSWERS 2020

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