Your immediate error message is probably caused by the fact that you're using the letter X
to indicate multiplication. It should be *
(the capital 8 character on US keyboards).
After you've solved that problem, you may find that you have many, many more results in the output than you expect. That's because you're not telling the database which record in CardiovascularRecords to "hook up" for the purpose of doing the calculation. That may or may not (probably not) produce the results you want.
If you're not getting what you want, you must tell us which column or columns in UserDetails "point to" the record in CardiovascularRecords that applies to any given calculation.
CREATE VIEW CardioCaloriesBurned AS
SELECT UserDetails.username AS username,
UserDetails.weight_in_pounds AS weight,
CardiovascularRecords.distance_in_miles AS distance,
((0.75 * weight_in_pounds) * distance_in_miles) AS caloriesBurned
FROM UserDetails INNER JOIN CardiovascularRecords
ON UserDetails.username = CardiovascularRecords.username