We are conducting a study to evaluate the progress of global health initiatives by analyzing changes in life expectancy across different countries. Specifically, we aim to identify which country experienced the greatest increase in life expectancy between the years $2015$ and $2020.$ This period is crucial for understanding the impact of various health policies and global events, such as the COVID$-19$ pandemic, on the population's health.

The database contains three tables: 'Countries', 'HealthIndicators', and 'HealthData'.

The 'Countries' table lists countries along with their respective regions.

The 'HealthIndicators' table includes various health metrics, one of which is life expectancy.

The 'HealthData' table records the values of these indicators for different countries across various years.

Provide an SQL query that identifies the country with the increase in life expectancy.

Use a CASE statement to handle values of life expectancy from $2015$ to $2020$:

If there are null values $-$ "Data Missing"

If the value is negative $-$ "Decrease"

if the value is positive $-$ Value of "increase$\_$in$\_$life$\_$expectancy" as a whole number