MySQL dynamic pivot table

Question

Im trying to get a pivot table with dynamic columns to work. When user_id is a string, it works fine but if its an int, then it seems to fail

Here is what I have so

Answer 1

Since the values are in int you are are making them the column names, you have to wrap the values in a backtick

The sql will look like:

max(case when user_id = 1 then score end) as `1`

The full query will be:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when user_id = ''',
      user_id,
      ''' then score end) AS `',
      user_id, '`'
    )
  ) INTO @sql
FROM  measure2;

SET @sql = CONCAT('SELECT inspection_date, ', @sql, ' 
                  FROM measure2 
                  GROUP BY inspection_date');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

See SQL Fiddle with Demo

Answer 2

Simple indeed - numbers alone aren't valid column names in SQL, so you need to amend your code to enclose them in backticks:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when user_id = ',
      user_id,
      ' then score end) AS `',
      user_id,
      '`'
    )
  ) INTO @sql
FROM  measure2;

SET @sql = CONCAT('SELECT inspection_date, ', @sql, ' 
                  FROM measure2 
                  GROUP BY inspection_date');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

I suggest retaining this change for string values as well, in case some of your string values match reserved words or include spaces.

(Also, ' aren't required around numeric values, so I have removed them from the case clauses.)

SQLFiddle here.