Question

我是SQL新手，我有一个基本问题。我有3个表和2个内部联接。这是我的SQL代码：

select   c.name, case when e.time > NOW() then 'Yes' else  'No' end AS "time" 
from table1 as e 
INNER JOIN table2 as a on e.id = a.id  
INNER JOIN table3 as c on a.id = c.id 
where e.conty= 'SAD'  
GROUP BY  c.name;

错误：must appear in the GROUP BY clause or be used in an aggregate function

Answer 1

要检索的任何字段都必须包含在该查询的GROUP BY子句中。您应在GROUP BY子句中包含“时间”，或将其从查询中排除。

select   c.name, case when e.time > NOW() then 'Yes' else  'No' end AS "time" 
from table1 as e 
INNER JOIN table2 as a on e.id = a.id  
INNER JOIN table3 as c on a.id = c.id 
where e.name = 'JOHN'  
GROUP BY  c.name, time;

Answer 2

在GROUP BY子句中使用e.time属性。

select c.name, case when e.time > NOW() then 'Yes' else  'No' end AS "time" 
from table1 as e 
INNER JOIN table2 as a on e.id = a.id  
INNER JOIN table3 as c on a.id = c.id 
where e.name = 'JOHN'  
GROUP BY c.name, e.time;

Answer 3

我猜您要聚合-以及最长时间：

__proto__

Answer 4

由于只选择带有group by name的行，因此不需要name = 'JOHN'。
如果要选择最大time的行，请执行以下操作：

select   
  'JOHN' name, 
  case when max(e.time) > NOW() then 'Yes' else  'No' end AS "time" 
from table1 as e 
INNER JOIN table2 as a on e.id = a.id  
INNER JOIN table3 as c on a.id = c.id 
where e.name = 'JOHN'

如何在PostgreSQL中使用两个内部联接的GROUP BY

4 个答案: