比较两个表列

Question

O/p from this Report- Subject Report / Displays all the science subject from report Subject /

SELECT `Contact Email Address`,
       `Studentname`,
       `TypeofSubjectLine`
FROM   `Subject`
WHERE  `TypeofSubjectLine`IN ('Science, Maths')  

Student Report

SELECT `studentreport`.`Contact Email Address`,
       CASE WHEN `subject`.`Contact Email Address` IS NOT NULL THEN 'new registration' 
       ELSE 'No New Registration' END AS NewRegistraion
FROM   `subject` LEFT JOIN `studentreport` 
ON `subject`.`Contact Email Address`=`studentreport`.`Contact Email Address`

Student email address which exists in Report- studentreport, only map those students who has subjects in Science and Maths ONLY (subject report). If the students subject is Science & Maths then their email address match and they are -"not new registration", if their email address do not match then they are "new registration" Please tell me what is wrong in my query ?

Answer 1

SELECT `studentreport`.`Contact Email Address`,
       CASE WHEN `subject`.`Contact Email Address` IS NOT NULL 
            THEN 'new registration' 
       ELSE 'No New Registration' END AS NewRegistraion
FROM   `subject` LEFT JOIN `studentreport` 
    ON `subject`.`Contact Email Address`=`studentreport`.`Contact Email Address`
WHERE  `TypeofSubjectLine`IN ('Science', 'Maths')