1. What data sources can Power BI connect to?

Ans: The list of data sources for Power BI is extensive, but it can be grouped into the following:
Files: Data can be imported from Excel (.xlsx, xlxm), Power BI Desktop files (.pbix) and Comma Separated Value (.csv).
Content Packs: It is a collection of related documents or files that are stored as a group. In Power BI, there are two types of content packs, firstly those from services providers like Google Analytics, Marketo, or Salesforce, and secondly those created and shared by other users in your organization.
Connectors to databases and other datasets such as Azure SQL, Database and SQL, Server Analysis Services tabular data, etc.


2. What are the different integrity rules present in the DBMS?

The different integrity rules present in DBMS are as follows:
Entity Integrity: This rule states that the value of the primary key can never be NULL. So, all the tuples in the column identified as the primary key should have a value.
Referential Integrity: This rule states that either the value of the foreign key is NULL or it should be the primary key of any other relation.


3. What are some common clauses used with SELECT query in SQL?

Some common SQL clauses used in conjuction with a SELECT query are as follows:
WHERE clause in SQL is used to filter records that are necessary, based on specific conditions.
ORDER BY clause in SQL is used to sort the records based on some field(s) in ascending (ASC) or descending order (DESC).
GROUP BY clause in SQL is used to group records with identical data and can be used in conjunction with some aggregation functions to produce summarized results from the database.
HAVING clause in SQL is used to filter records in combination with the GROUP BY clause. It is different from WHERE, since the WHERE clause cannot filter aggregated records.


4. What is the difference between count, counta, and countblank in Excel?

The count function is very often used in Excel. Here, let’s look at the difference between count, and it’s variants - counta and countblank.

1. COUNT
It counts the number of cells that contain numeric values only. Cells that have string values, special characters, and blank cells will not be counted.

2. COUNTA
It counts the number of cells that contain any form of content. Cells that have string values, special characters, and numeric values will be counted. However, a blank cell will not be counted.

3. COUNTBLANK
As the name suggests, it counts the number of blank cells only. Cells that have content will not be taken into consideration.