mysql - 数据库行需要显示在列中

Question

我有下面的数据库表:

id       Creation_Date         Goals  Alternative    Value
-----------------------------------------------------------
1   2014-04-17 10:09:30         G1         A         0.86
2   2014-04-17 10:09:30         G1         B         0.87
3   2014-04-17 10:09:30         G2         A         0.5
4   2014-04-17 10:09:30         G2         B         0

我正在触发以下查询:

  select 
    alternative,
    max( case when goals='G1' then round( value, 2 ) end ) as 'G1',
    max( case when goals='G2' then round( value, 2 ) end ) as 'G2'
    from sgwebdb.dim_module
  group by alternative
  ;

并获得以下输出:

 Alternative    G1       G2
-----------------------------
 A            0.86      0.50    
 B            0.87      0.00

现在没有预先定义目标(G1、G2、G3、G4……)，它可以是任何数字。我可以有一个查询，以便在不在查询中定义多个目标的情况下获得相同的输出吗？

Answer 1

这样的事情可能会起作用:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'MAX(IF(goals = ''',
      goals,
      ''', round(value, 2), NULL)) AS ',
      goals
    )
  ) INTO @sql
FROM sgwebdb.dim_module;
SET @sql = CONCAT('SELECT alternative, ', @sql, ' FROM sgwebdb.dim_module GROUP BY alternative');

prepare stmt from @sql;
execute stmt;

来源:http://buysql.com/mysql/14-how-to-automate-pivot-tables.html

SQL fiddle :http://sqlfiddle.com/#!2/ac9f88/10