返回所有字段时，在列中选择唯一值

Question

SELECT tblDTR.emp_id,
       tblEmployee.first_name,
       tblEmployee.last_name,
       tblDTR.time_out,
       tblDTR.time_in
FROM   tblDTR
INNER JOIN
       tblEmployee
ON     tblDTR.emp_id = tblEmployee.emp_id
WHERE  (((tblDTR.current_date)=#9/3/2015#));

我只希望记录只包含唯一ID和最早 time_in值，例如：

EMP1234 - 12:00 AM
EMP12 - 12:45 AM
EMP1 - 7:30 AM (not 12:50 PM)

......按时间顺序排列。

Answer 1

仅当不存在具有相同emp_id的旧行时，才使用SELECT t1.emp_id, tblEmployee.first_name, tblEmployee.last_name, t1.time_out, t1.time_in FROM tblDTR t1 INNER JOIN tblEmployee ON t1.emp_id = tblEmployee.emp_id WHERE (((t1.current_date)=#9/3/2015#)) and NOT EXISTS (select 1 from tblDTR t2 where t2.emp_id = t1.emp_id and t2.time_in < t1.time_in) 返回行：

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