Question

I can select the number of rows returned by a query when I select everything by doing the following:

SELECT Count(*) FROM `foo`.`bar`;

However, I now want to select how many columns are returned. Is there an easy way to do this?

Answer 1

Use the information_schema database.

SELECT 
  COUNT(COLUMN_NAME) AS numcols
FROM COLUMNS
WHERE 
  TABLE_NAME = 'bar'
  AND TABLE_SCHEMA = 'foo'

To put the two together, use:

SELECT
  (SELECT COUNT(*) FROM foo.bar) AS numrows,
  (SELECT 
      COUNT(COLUMN_NAME) AS numcols
    FROM COLUMNS
    WHERE 
      TABLE_NAME = 'bar'
      AND TABLE_SCHEMA = 'foo'
  ) AS numcols