SQL检查来自多行的id值

Question

我想基于某个条件来计算id的数量。

我有一个包含3列的表：id（不唯一），foo（整数）和bar（字符串）。

    id| foo | bar   
     1|  0  | yes    
     1|  1  | no
     1|  1  | no    
     2|  0  | no  
     2|  1  | no    
     3|  0  | yes
     3|  1  | no
     3|  2  | yes
     4|  0  | yes  

我希望查询给我一个id列表。条件：

a. id should have more than 1 entry.  
b. id needs to have foo = 0 AND bar = yes.  
c. if (b) is satisfied, it also needs to have all the rest of foo to have bar = no. (the number of foo for each id is unknown)

在上面的示例中，查询应该返回id = 1.（Id = 2是 无效，因为当= foo = 0时bar = no.Id = 3因为bar而无效 =当foo = 2时是。）

Answer 1

您可以使用id和group by获取having的列表。您的条件的确切翻译是：

select id
from t
group by id
having count(*) > 1 and
       sum( foo = 0 and bar = 'yes' ) = 1 and
       sum( bar = 'no' ) = count(*) - 1;

如果您想要计数而不是列表，则可以使用子查询。