Question

我想根据我的条件显示其他列。我的条件基于类型。但是当我在条件时使用以下情况时，我似乎检索一行带有硬编码值，每行匹配一行。不匹配有1个空行。在条件

时，我似乎无法弄清楚我的错误

select t1.id,   
  case when   
  t2.value like 'App%'  
  then 'Fruit'  
  end as 'Fruit'  
  case when 
  t2.value like 'Car%'  
  then 'Veggie'  
  end as 'Veggies'  
  case when 
  t3.value = 'Skittles' 
  then 'Candy'  
  end as 'Candy' 
where t1.id = t2.id  
and t1.id=t3.id

T1：

T2：

ID(fk)   value  
1        Apple  
1        Orange  
2        Carrot  
3        Berry  
3        Melon

T3：

ID (fk) value  
4        Mars
5        Twix
6        Skittles
7        Milkyway

期望的输出：

ID         Fruits     Veggies       Candy    
1          Fruit  
2                      Veggie  
3                            
4                                      
5                                      
6                                    Candy  
7                                       
8                       
9

当前输出错误：

ID         Fruits     Veggies       Candy    
1          Fruit    
1  
2                      Veggie    
2  
3                            
4                                       
5                                     
6                                    Candy   
6  
7     
8                       
9

Answer 1

select 
  t1.id,   
  CASE WHEN SUM(CASE WHEN t2.value like 'App%' THEN 1 END) > 0
       THEN 'Fruit'  
  END as 'Fruit',
  CASE WHEN SUM(CASE WHEN t2.value like 'Car%' THEN 1 END) > 0
       THEN 'Veggie'  
  END as 'Veggies',
  CASE WHEN SUM(CASE WHEN t2.value like 'Skittles' THEN 1 END) > 0
       THEN 'Candy'  
  END as 'Candy'  

where t1.id = t2.id  
  and t1.id = t3.id  

GROUP BY t1.id

如何根据where条件创建新列

1 个答案: