Question

I have a table similar to the following:

value    unit
-----    -----
100      cm
30       in
120      cm
35       in
37       in
29       in

In my selection, I’d like to convert inches to centimeters. Something like the following:

SELECT AVG(unit = in ? value*2.54 : value) FROM data_table;

What is the proper syntax, or method to perform this type of selection in MySQL?

Answer 1

SELECT AVG(value) FROM (
  SELECT
    CASE unit
      WHEN "cm" THEN value
      WHEN "in" THEN value*2.54
      END AS value
    FROM data_table
) AS all_in_cm