patternsqlMinor
Exclude dataset from a query
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datasetfromqueryexclude
Problem
I have 2 tables
Primary key for both tables are (
When a student wants to take an exam, then we write one row in
But if a student passed an exam and is not satisfied, then he wants to cancel the exam and we need to write one row in table
My question is: How to select just non-canceled exams from table
EXAM(StudentID, SubjectID, SchoolYear, Period, Mark) and
CANCELED_EXAM (StudentID, SubjectID, SchoolYear, Period).
Primary key for both tables are (
StudentID, SubjectID, SchoolYear, Period).When a student wants to take an exam, then we write one row in
EXAM table.But if a student passed an exam and is not satisfied, then he wants to cancel the exam and we need to write one row in table
CANCELED_EXAM.My question is: How to select just non-canceled exams from table
EXAM.Solution
This is standard SQL
SELECT
*
FROM
EXAM E
WHERE
NOT EXISTS (SELECT *
FROM
CANCELED_EXAM CE
WHERE
E.StudentID = CE.StudentID AND
E.SubjectID = CE.SubjectID AND
E.SchoolYear = CE.SchoolYear AND
E.Period = CE.Period )Code Snippets
SELECT
*
FROM
EXAM E
WHERE
NOT EXISTS (SELECT *
FROM
CANCELED_EXAM CE
WHERE
E.StudentID = CE.StudentID AND
E.SubjectID = CE.SubjectID AND
E.SchoolYear = CE.SchoolYear AND
E.Period = CE.Period )Context
StackExchange Database Administrators Q#3896, answer score: 6
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