Question

I’m working with a relational database that uses SQL99.

I have a series of 10 columns, each of the 10 columns contain a number value.

I need to sum each column individually and then take those sums and add them all together to get an overall sum. Then I must divide the overall sum by 15.

I’ve tried every format I can think of and have yet to return any results. I have no idea what the syntax should look like.

Answer 1

SELECT SUM(subsum) / 15 FROM (
   SELECT SUM(column1) AS subsum
      FROM table
     UNION ALL
    SELECT SUM(column2) AS subsum
      FROM table
     UNION ALL
    ...
    SELECT SUM(column10) AS subsum
      FROM table
)