sql重复记录查询

Question

我有两张桌子。

1. MasterStudent (student_number,name,address,dob)
2. 登机点（登机ID、学生编号、分区数）

我想在生日之前得到重复的学生，但我不知道如何得到重复的记录。我是 sql 新手。我试过这个查询：

SELECT T.GivenName + ' ' + T.SurName AS Name,
  T.StreetNumber + ' ' + T.StreetName + ' ' + T.Suburb + ' ' + T.PostCode + ' ' + T.State + ' ' + T.Country AS Address,
  T.Sex, 
  T.DateOfBirth,
  T.yearlevel AS Year,
  z.dupCount,
  T.StudentNumber
FROM tblMasterStudent AS T
INNER JOIN (SELECT DateOfBirth, COUNT(*) AS dupCount
            FROM tblMasterStudent
            GROUP BY DateOfBirth
            HAVING (COUNT(*) > 1)) AS z ON z.DateOfBirth = T.DateOfBirth
            ORDER BY z.dupCount DESC

它正在从 MasterStudent 表中按生日获取重复记录，但我想从 masterStudent+BoardingPoint 获取记录

Answer 1

您可以按生日分组并查看多次出现的所有生日：

SELECT count(1) as frequency, dob
FROM students
GROUP BY dob
HAVING frequency > 1;