Hello students In this article we will discuss about the important Informatics practics Viva question. We will Discuss about very hot question for Practical viva. You must know about these questions. These questions are very important viva as well as term examination. These days you are preparing for your class 12 cbse practical examination and you are worry about how face external examiner and which question he/she will ask from you. we know your situation and pressure of cbse practical examination on you. Don't worry release your pressure we will provide important question related to your practical examination. After preparing these question you will surely get 90% -100 % marks in your practical examination 2021-2022. We will share important question in multiple sets. Today I will share set 1.
SET 1
Question 1. What do you understand by Null in mysql ?
Answer: The NULL value means “no data.” NULL can be written in any lettercase. Be aware that the NULL value is different from values such as 0 for numeric types or the empty string for string types
Question2. Write sql query to create table, with constrains, keys .
Answer: create table table_name( EMPID varchar(10) primary key, name varchar(255) not null);
Question3. What is difference between mysql and sql ?
Answer: SQL is a query programming language that manages RDBMS. MySQL is a relational database management system that uses SQL
Question4. What is the difference between DDL and DML commands in Mysql ?
Answer:Difference between DDL and DML:
| DDL | DML |
|---|---|
| It stands for Data Definition Language. | It stands for Data Manipulation Language. |
| It is used to create database schema and can be used to define some constraints as well. | It is used to add, retrieve or update the data. |
| It basically defines the column (Attributes) of the table. | It add or update the row of the table. These rows are called as tuple. |
| It doesn’t have any further classification. | It is further classified into Procedural and Non-Procedural DML. |
| Basic command present in DDL are CREATE, DROP, RENAME, ALTER etc. | BASIC command present in DML are UPDATE, INSERT, MERGE etc. |
| DDL does not use WHERE clause in its statement. | While DML uses WHERE clause in its statement. |
Question5. What is the use of Group by command ?
Answer: The SQL GROUP BY clause is used in collaboration with the SELECT statement to arrange identical data into groups.
Question6. What is the difference between Where clause and Having clause ?
Answer: The main difference between them is that the WHERE clause is used to specify a condition for filtering records before any groupings are made, while the HAVING clause is used to specify a condition for filtering values from a group.
Question7. What is the difference between Group by and Order by ?
Answer: Group by statement is used to group the rows that have the same value. Whereas Order by statement sort the result-set either in ascending or in descending order.
Question8. What is the difference between count(*) count()?
Answer: COUNT(*) counts the rows in your table. COUNT(column) counts the entries in a column - ignoring null values
Question9. What is the difference between single row function and multi row function/aggregate function?
Answer:
Single Row functions - Single row functions are the one who work on single row and return one output per row. For example, length and case conversion functions are single row functions.
Multiple Row functions - Multiple row functions work upon group of rows and return one result for the complete set of rows. They are also known as Group Functions.
Question10. What is the difference between alter and update command?
Answer: ALTER Command is used to add, delete, modify the attributes of the relations (tables) in the database. UPDATE Command is used to update existing records in a database
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