'How to get average of multiple variables

Table name: products,

column names: rice_price, sugar_price

I would like to get the average of both columns separately. For example;

SELECT
  AVG(rice_price) avg_rice,
  AVG(sugar_price) avg_sugar
FROM
  products

If I run this query on SQL server, I get the message below

Msg 8117, Level 16, State 1, Line 4 Operand data type nvarchar is invalid for avg operator.

What could be the solution?

sql sql-server

Sources

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