从内部联接中选择列

Question

I wanted to select two columns from inner join of two select queries. I have written a query joining three tables and from the result I want to get only two column. But my query is showing error.I am using oracle sql developer.

SELECT firstname,surname
FROM (
SELECT A.firstname,A.surname,I.ACNUM,I.FIELDNUM 
FROM ACADEMIC A INNER JOIN INTEREST I
ON (A.ACNUM = I.ACNUM)
INNER JOIN SUBJECT S ON (I.FIELDNUM = S.FIELDNUM) WHERE S.TITLE = 'History' ) ;

I want only the firstname and surname but I am getting error like:

Incorrect syntax near ';'.

Answer 1

Why are you using a subselect? Just use:

SELECT A.firstname, A.surname
FROM ACADEMIC A INNER JOIN
     INTEREST I
     ON A.ACNUM = I.ACNUM INNER JOIN
     SUBJECT S
     ON I.FIELDNUM = S.FIELDNUM
WHERE S.TITLE = 'History' ;

Answer 2

When you select from query you should name it as well. Try this:

SELECT D.firstname,D.surname
  FROM (SELECT A.firstname,A.surname,I.ACNUM,I.FIELDNUM
  FROM ACADEMIC A
         INNER JOIN INTEREST I ON (A.ACNUM = I.ACNUM)
         INNER JOIN SUBJECT S ON (I.FIELDNUM = S.FIELDNUM)
  WHERE S.TITLE = 'History') D;