排除选择重复项

Question

有一个表： prov_dl

| ID | Code     | Value |
+----+----------+-------+
| 2  | PRC      | 0,1701|
| 2  | Stad     | 3     |   

数据以这种形式存储，即
按代码有几个条目 您需要以这种形式提取数据：

  | ID | Stadya   | Percent   |
  +----+----------+-----------+
  | 2  | 3        | 0,1701    |    

我尝试：

select id,
case when code='Stad' then Value  end Stadya,
case when code='PRC'  then  Value end Percent  
from prov_dl

| ID | Stadya   | Percent|
+----+----------+--------+
| 2  |          | 0,1701 |
| 2  |   3      |        | 

Answer 1

使用max（）

    select id,
    max(case when code='Stad' then Value  end) as Stadya,
    max(case when code='PRC'  then  Value end) as Percent  
    from prov_dl group by id