在php mysql中水平显示结果

Question

如何实现以横向方式显示结果？
   如我的数据库中显示，我有3个字段。主题，结果，期间    我计划只创建period1，period2，period3，period4字段
   为每个时期节省价值，但我不认为这是不可取的。

sample database:  
subject    |  result    |    period   |
--------------------------------------  
 eng       |   100      |      1      |  
 lit       |   95       |      1      |  
 eng       |   95       |      2      |  
 lit       |   86       |      2      |  
 eng       |   92       |      3      |  
 lit       |   88       |      3      |     


subject  |  period1  |  period2  |  period3  |  period4  |  
-----------------------------------------------------------  
eng      |    100    |   95      |     92    |           |  
lit      |    95     |   86      |     88    |           |  

hope you can help mo guys. thank you in advance.

Answer 1

快速直接的解决方案：

select 
    aggr.subject, 
    max(aggr.period1), 
    max(aggr.period2), 
    max(aggr.period3), 
    max(aggr.period4) 
from (
    select 
        subject as subject, 
        result as period1, 
        0 as period2, 
        0 as period3, 
        0 as period4 
    from test 
    where period = 1 
    union 
    select 
        subject, 
        0, 
        result, 
        0, 
        0 
    from test 
    where period = 2 
    union 
    select 
        subject, 
        0, 
        0, 
        result, 
        0 
    from test 
    where period = 3 
    union 
    select 
        subject, 
        0, 
        0, 
        0, 
        result 
    from test 
    where period = 4
) aggr group by aggr.subject;