MySQL的：獲取有一個id爲一年中的所有記錄，但不是另一個

Question

我有一個表：

HOST_ID | ContractYear 
1  | 2008 
2  | 2008 
3  | 2008 
1  | 2009 
4  | 2009 

我需要的是一個查詢，會告訴我所有的HOST_ID的是，2009年是不。

上例中的答案是HOST_ID = 4。

謝謝。

Answer 1

select 
    HOST_ID 
from 
    table_name 
where 
    ContractYear = 2009 
    AND HOST_ID NOT IN (select HOST_ID from table_name where ContractYear = 2008) 

Answer 2

用途：

SELECT t.host_id 
    FROM TABLE t 
WHERE t.contractyear = 2009 
    AND NOT EXISTS(SELECT NULL 
        FROM TABLE t2 
        WHERE t2.host_id = t.host_id 
        AND t.contractyear = 2008) 

Answer 3

SELECT DISTINCT host_id 
FROM mytable mo 
WHERE ContractYear = 2009 
     AND NOT EXISTS 
     (
     SELECT NULL 
     FROM mytable mi 
     WHERE mi.host_id = mo.host_id 
       AND ContractYear = 2008 
     ) 

Answer 4

更通用的，因爲它過濾出所有不屬於你正在尋找

select HOST_ID 
from table t 
where ContractYear = 2009 
and HOST_ID not in (select distinct HOST_ID 
        from table t2 
        where t.ContractYear != t2.ContractYear)