Question

My ultimate goal is to create a pivot-table view in MySQL with dynamic columns based on the contents of another table. At the moment I am trying to continue on from where artfulsoftware leaves off; right now I can query for results that give me my desired column names. Unfortunately I’m lost on how to actually use the results as column names in a SELECT statement. I suspect that MySQL variables will be helpful, but I can’t figure it out.

To clarify the problem, say I have a table like:

+---------------------------------------------------+
| countpivotarg                                     |
+---------------------------------------------------+
| ,SUM(IF(domain = "test.com",1,0)) AS `test.com`   |
| ,SUM(IF(domain = "test2.com",1,0)) AS `test2.com` |
+---------------------------------------------------+

I want to create a select statement that looks like:

SELECT id,
       meta_id,
       SUM(IF(domain = "test.com",1,0)) AS `test.com`,
       SUM(IF(domain = "test2.com",1,0)) AS `test2.com`
FROM   myTable;

How do I go about doing that?

Answer 1

You may use MySQL Server prepared statements for building dynamic queries from string variables.

Example:

SELECT domain INTO @colname FROM myTable LIMIT 1;
SET @s = CONCAT('SELECT `',@colname,'` FROM myTable');
PREPARE stmt FROM @s;
EXECUTE stmt;

Note: backticks are required in case column names contain spaces.