如何编写查询选择值而不重复相同的值？

Question

我需要从此表中选择employee_id，如果有00001是四次，我只需要获取一次。

如何为此方案编写查询？

id  company_ID  Employee_ID Name        Relationship    Dob     Age Gender       
    1   EMPL        00001       Choodamani  Spouse      11-Aug-66   49  Female            
    2   EMPL        00001       Komala      Mother      30-Oct-39   76  Female            
    3   EMPL        00001       Varshini    Daughter    29-Apr-04   11  Female            
    4   EMPL        00001       Vasudevan   Employee    15-Jul-62   53  Male    
    5   EMPL        00002       Siddharth   Son         1-Jun-00    15  Male              
    6   EMPL        00002       Poongavanam Mother      21-Oct-39   76  Female            
    7   EMPL        00002       Aruna       Spouse      16-Sep-68   47  Female            
    8   EMPL        00002       Abirami     Daughter    7-May-97    18  Female            
    9   EMPL        00002       Murali      Employee    7-Oct-67    48  Male

Answer 1

您可以使用distinct关键字：

SELECT DISTINCT Employee_ID FROM Employees

Answer 2

您可以尝试distinct：

select distinct Employee_ID from tbl

Answer 3

select DISTINCT Employee_ID from tablename