Question

我是2个mysql表，第一个表Activity将患者活动级别存储为整数，另一个表将每个整数与描述相映射。我正在尝试创建一个选择查询，它给出了患者活动的描述，而不是整数值。

Activity Table
id|pid|bathing|cognition|housekeeping|dressing|feeding|meal
1 | 20|  4    |   4     |      2     |    6   |   8   |   4
2 | 40|  4    |   2     |      4     |    4   |   6   |   6  

Mapping Table
value|description
2    | Independent
4    | Minimal 
6    | Moderate
8    | Maximum

Desired Query Result

id|cid|bathing|cognition|housekeeping|dressing|feeding|meal
1 | 20|Minimal|Minimal  |Independent |Moderate|Maximum|Minimal

我已经研究过使用mysql [CASE] [1]，但这似乎不起作用。我还回顾了这两个stackoverflow问题[问题1] [2]和[问题2] [3]他们似乎并不是我想要的。任何帮助将不胜感激。

Answer 1

以下代码使用您的映射表来显示正确的描述。选择subquery上的MYSQL文档。

Select id, pid,
(Select description from mapping where value=a.bathing) as 'bathing',
(Select description from mapping where value=a.cognition) as 'cognition',
(Select description from mapping where value=a.housekeeping) as 'housekeeping',
(Select description from mapping where value=a.dressing) as 'dressing',
(Select description from mapping where value=a.feeding) as 'feeding',
(Select description from mapping where value=a.meal) as 'meal'
From activity a

Answer 2

使用左连接的另一种方法：

select 
  id, 
  pid, 
  m1.description as bathing,
  m2.description as cognition,
  m3.description as housekeeping,
  m4.description as dressing,
  m5.description as feeding,
  m6.description as meal
from activity
left join mapping m1 on m1.value = bathing
left join mapping m2 on m2.value = cognition 
left join mapping m3 on m3.value = housekeeping 
left join mapping m4 on m4.value = dressing 
left join mapping m5 on m5.value = feeding 
left join mapping m6 on m6.value = meal

Sample SQL Fiddle

使用MySQL，可能无法为每个具有映射值的列加入映射表一次。（在MSSQL上，您可以使用unpivot/pivot代替（example））。

MySQL选择 - 根据映射表显示结果

2 个答案: