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我有一個表單，它在提交時會將輸入的數據輸出到表單中，並將其輸出到查詢結果中。如果文本框爲空，它將搜索該特定字段的所有數據。目前我的查詢輸出：查詢輸出比它應該做的更多的行，這是爲什麼？
SessionId ModuleId CourseId ClassId StudentUsername TeacherUsername Grade
ABB CHT2520 INFO101 104 u0867587 m.prigmore A
ABB CHI2550 INFO101 101 u0867587 j.lu A
ABB CHI2550 INFO101 104 u1231231 j.lu F
ABB CHT2520 INFO101 101 u1231231 m.prigmore F
NVK CHI2550 INFO101 101 u0867587 j.lu F
RMI CHI2565 INFO101 102 u0660663 j.forden F
它正在輸出更多的行，然後它應該這樣做。一個學生屬於同一個班級的一個單元。問題在於它顯示一個學生屬於兩個班級，因爲一個模塊不正確。它這樣做的原因是因爲它根據學生正在學習的模塊來識別學生所在的班級。
因此，如果模塊'CHI2550'有兩個班級，任何需要模塊'CHI2550'的學生被分配到兩個班級，但應該是一個班級的學生被分配到一個班級，並且應該由'StudentClass'表。問題是，如果我在其中一個JOINS中包含'StudentClass'，則查詢輸出9行。
查詢應的輸出這樣的：
SessionId ModuleId CourseId ClassId StudentUsername TeacherUsername Grade
ABB CHI2550 INFO101 101 u0867587 j.lu A
ABB CHI2550 INFO101 104 u1231231 j.lu F
NVK CHT2520 INFO101 103 u0867587 m.prigmore F
RMI CHI2565 INFO101 102 u0660663 j.forden F
我怎樣才能得到查詢到輸出上面的結果呢？下面是查詢：
下面是每個表和它們的數據（因爲我所面臨的問題，最重要的表是StudentClass，班，學生，模塊）：
Course Table:
CourseId CourseName Duration
INFO101 Bsc Information Communication Technology (ICT) 3/4
CourseModule Table:
CourseId ModuleId
INFO101 CHI2550
INFO101 CHI2565
INFO101 CHT2520
Module Table:
ModuleId ModuleName Credits
CHT2520 Advanced Web Programming 20
CHI2565 E-Commerce Business and Technology 20
CHI2550 Modern Database Applications 20
Session Table:
SessionId ModuleId Semester SessionDate SessionTime TeacherId Room Building
NVQ CHT2520 Spring 2011-03-21 13:00:00 T2 CW2/04 Canalside West
NVK CHT2520 Fall 2011-11-10 10:00:00 T2 CW2/04 Canalside West
RMI CHI2565 Fall 2011-09-13 12:00:00 T5 CW5/01 Canalside West
RMT CHI2565 Spring 2011-03-29 14:00:00 T2 CW2/04 Canalside West
ABB CHI2550 Spring 2011-03-15 12:00:00 T1 CW4/10 Canalside West
ABH CHI2550 Summer 2011-05-03 15:00:00 T4 CW4/10 Canalside West
Grade_Report Table:
StudentId SessionId Grade Mark
S1 NVK F 5
S2 ABB A 80
S1 ABB A 80
S3 RMI F 0
Student Table:
StudentId StudentForename StudentSurname Year StudentUsername CourseId
S1 Mayur Patel 3 u0867587 INFO101
S2 Jim Carlton 3 u1231231 INFO101
S3 Ahmed Seedat 3 u0660663 INFO101
S4 Amar Barot 3 u0954857 INFO101
S5 Richard Davies 3 u0877223 INFO101
StudentClass Table:
ClassId StudentId
101 S1
102 S3
103 S1
104 S2
Class Table:
ClassId Room ClassDay ClassTime ModuleId CourseId TeacherId
101 CW4/10 Thursday 10:00:00 CHI2550 INFO101 T1
102 CW5/01 Wednesday 12:00:00 CHI2565 INFO101 T5
103 CW2/04 Monday 15:00:00 CHT2520 INFO101 T2
104 CW4/10 Thursday 11:00:00 CHI2550 INFO101 T1
Teacher Table:
TeacherId TeacherForename TeacherSurname TeacherUsername TeacherPassword
T1 Joan Lu j.lu scomp21
T2 Martyn Prigmore m.prigmore prigmore36
T3 Arshard Ali a.ali aliict
T4 Paul Judge p.judge data01
T5 John Forden j.forden hudds_10