Access | Advanced queries exercise | Expressions - error in population density
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Open the database in the above folder.
Create a new field called Density which calculates the population density of each country (in a moment we will compare this with the one which is already in the table):
Density is equal to Population/SquareMiles
Save this query as PopulationDensity, then close it down.
Create another query based on the first one which includes a new field showing the error between the PeoplePerSquareMile field report and the Density field that you have calculated:
Use the ABS function to return the absolute value of the error
Sorting as above should revealt that the biggest error reported is for Libya, but that most countries' population densities are correctly calculated.
Save your query as PopulationDensityErrors, then close it and the database down.