SELECT C.COURSE_ID, TITLE, A.STUDENT_ID, COMPANY_ID, AD.ADDRESS
FROM COURSE C, STUDENT S, ADDRESS AD, ATTENDANCE A
WHERE C.COURSE_ID = AD.COURSE_ID
AND AD.ADDRESS = A.ADDRESS
AND A.STUDENT_ID = S.STUDENT_ID
AND COMPANY_ID IS NOT NULL;

I have got 4 tables and this query does all it needs to except that i have to include the ADDRESS not present in the Attendance table. For example

ADDRESS TABLe          ATTENDANCE table
Address                  Address
  a                         a
  b                         b
  c
  d

So i want the end result to show:

COURSE ID    TITLE   STUDENT_ID   COMPANT_ID   ADDRESS
   BLA        BLA      BLA         BLA           a
   BLA        BLA      BLA         BLA           b
   BLA        BLA      BLA         BLA           c
   BLA        BLA      BLA         BLA           d

While the query above shows the same result but excluding c and d present in 'address' column.

Sorry if i'm not clear enough. Thank you

有帮助吗?

解决方案

If you change your query to use an LEFT JOIN to join the ATTENDANCE table it will exclude all records not present in it that are in the ADDRESS table

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