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我有一个评估结果数据库，其中包含确定学生、年级、年份和学期的字段。下面的查询找到了在某个起点和终点对特定主题进行评估的学生：

SELECT
  a1.PupilId
FROM assessment as a1
  JOIN assessment as a2
    USING (PupilId)
WHERE a1.GradeID in('1A','1B','1C')
    AND a2.GradeID in('5A','5B','5C')
    AND a1.NCYear = '1'
    AND a1.Term = '6'
    AND a2.NCYear = '2'
    AND a2.Term = '6'
    AND a1.Subject = '31'
    AND a2.Subject = '31'
    AND a1.Type = 'assessment'
    AND a2.Type = 'assessment'

这很好用，但现在我想找到具有起始年级（即 NCYear='1' 和 Term='6'）但没有最终成绩条目的学生。我玩过NOT EXISTS，但无法让它工作。

为了澄清，这是评估表：

id | Subject | PupilId | NCYear | Term | GradeID | Type
--------------------------------------------------------
1  | 31      | 1       | 1      | 6    | 1A      | assessment
2  | 31      | 1       | 2      | 6    | 5A      | assessment
3  | 31      | 2       | 1      | 6    | 1A      | assessment

上面的 SQL 查询应该返回 PupilID 1。我需要返回 PupilID 2 的查询，开始评估在那里但没有结束评估。

有什么建议么？

4

2 回答 2

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用 if 试试这个查询

SELECT
  a1.PupilId
FROM assessment as a1
  JOIN assessment as a2
    USING (PupilId)
WHERE a1.GradeID in('1A','1B','1C')
    AND a2.GradeID in('5A','5B','5C')
    AND a1.NCYear = '1'
    AND a1.Term = '6'
    AND a2.NCYear = '2'
    AND a2.Term = '6'
    AND a1.Subject = '31'
    AND a2.Subject = '31'
    AND a1.Type = 'assessment'
    AND a2.Type = 'assessment'
    AND IF(a1.NCYear = 1, IF(a1.Term = 6,a2.GradeID IS NULL,1),1)
于 2013-01-25T18:41:09.257 回答
0

您需要使用 OUTER JOIN：

SELECT
  a1.PupilId
FROM assessment as a1
  OUTER JOIN assessment as a2
    ON a2.PupilId = a2.PupilId AND a2.NCYear = '2' AND a2.GradeID in('5A','5B','5C') AND a2.Term = '6' AND a2.Subject = '31' AND a2.Type = 'assessment'        
WHERE a1.GradeID in('1A','1B','1C')
    AND a1.NCYear = '1'
    AND a1.Term = '6'
    AND a1.Subject = '31'
    AND a1.Type = 'assessment'
    AND a2.PupilId IS NULL
于 2013-01-25T18:56:45.640 回答