Postgresql 如何比较postgres中的两个字段？

我有一张表叫登记表。学生A有3条记录，其中两条记录的开始日期相同

我想找到所有2013年开始日期相同的研究生

注册人数：

StudentID   Start_Date      Syear school_id
1             2013-06-21    2013    10
1             2013-06-21    2013    11 
1             2014-02-21    2014    10 

提前谢谢

SELECT StudentID, Start_Date
FROM
(
    SELECT StudentID, Start_date, COUNT(*) OVER (PARTITION BY start_date) count
    FROM Student
)
WHERE count > 1

或

SELECT StudentID, Start_Date
FROM Student S1
WHERE EXISTS (
    SELECT *
    FROM Student S2
    WHERE S1.Start_Date = S2.Start_Date AND S1.StudentID <> S2.StudentID
)