Explanation:

Comprehensive Detailed Explanation
We need to query a KQL database table named Readings to generate output that includes both the current reading and the previous reading values and datetime for each row.
Step 1: Understanding Requirements
The output table shows:
City, Area, MeterReading, Datetime
PrevMeterReading, PrevDatetime
The prev() function in KQL is used to access the value of a column from the previous row (based on order).
Step 2: Query Construction
We start with filtering:
Readings
| where City == " Copenhagen "
| sort by Datetime
To add columns that calculate the previous reading and previous datetime, we use extend:
| extend PrevMeterReading = prev(MeterReading), PrevDatetime = prev(Datetime) extend creates new columns.
prev() pulls the previous row's values.
Finally, we only want specific columns in the output. For this, we use project:
| project City, Area, MeterReading, Datetime, PrevMeterReading, PrevDatetime Step 3: Completed Query Readings
| where City == " Copenhagen "
| sort by Datetime
| extend PrevMeterReading = prev(MeterReading), PrevDatetime = prev(Datetime)
| project City, Area, MeterReading, Datetime, PrevMeterReading, PrevDatetime Why This is Correct extend adds calculated columns.
prev() gives access to the previous row.
project selects only the required columns.
This matches exactly the table shown in the question.
References
Kusto Query Language - extend operator
Kusto Query Language - project operator
prev() function in KQL

Explanation:

Comprehensive Detailed Explanation
We are tasked with writing a T-SQL query to denormalize the tables Employee and Contract in a Fabric warehouse.
Requirements Breakdown
Include attributes from matching rows in the Contract table
This means we must join Employee and Contract on EmployeeID.
Ensure that all rows from the Employee table are preserved
This requires a LEFT OUTER JOIN from Employee to Contract. If an employee has no contract, we still want the employee record included.
Return the total number of employees per contract type for all contract types that have more than two employees This means we need to:
Group by ContractType
Count distinct EmployeeID
Filter groups where that count > 2.
To filter aggregated results, we use HAVING, not WHERE.
Completed Query
WITH result AS (
SELECT
e.EmployeeID,
e.EmployeeName,
e.EmployeePosition,
c.ContractType,
c.StartDate
FROM Employee AS e
LEFT OUTER JOIN Contract AS c
ON c.EmployeeID = e.EmployeeID
)
SELECT
ContractType,
COUNT(DISTINCT EmployeeID) AS TotalEmployees
FROM result
GROUP BY ContractType
HAVING COUNT(DISTINCT EmployeeID) > 2;
Why This is Correct
LEFT OUTER JOIN ensures all employees are included, regardless of contracts.
HAVING allows filtering aggregated groups by employee counts.
The query returns ContractType, StartDate (as requested in denormalization), and aggregated employee counts.
References
T-SQL JOINs in Microsoft Fabric
Aggregate functions and HAVING clause
Denormalization best practices in Fabric warehouses

The Python code and output shown in the exhibit display a histogram, which is a representation of the distribution of data. This kind of analysis is descriptive analytics, which is used to describe or summarize the features of a dataset. Descriptive analytics answers the question of " what has happened " by providing insight into past data through tools such as mean, median, mode, standard deviation, and graphical representations like histograms.
References: Descriptive analytics and the use of histograms as a way to visualize data distribution are basic concepts in data analysis, often covered in introductory analytics and Python programming resources.