Mysql查詢選擇具有不同列值的結果

Question

我有一張展示書籍的桌子。 但是，我希望每個唯一的電子郵件地址（ strContactEmail ）只顯示一本書。 我嘗試了下面的查詢，它沒有用。 任何幫助非常感謝

$sql =  "SELECT lngbookid, strTitle, strAuthor, strcoursecode, strISBN, ".
        " strcontactname, DISTINCT(strContactEmail) AS strContactEmail, ".
        " curPrice, ysnsalerent, dtmpostdate, memcomments, school, ".
        " ASIN, BookIMG, ISBN10, ISBN13, Updated, ".
        " datetime, user_ip, NoOtherBooks ".
        " FROM tblbooks ".
        " WHERE strcoursecode LIKE '%$search%'  ".
        " ORDER BY datetime DESC LIMIT 50";

Answer 1

嘗試GROUP BY語句：

http://www.w3schools.com/sql/sql_groupby.asp

Answer 2

最簡單的方法：

 
 
 
 
  
  
  SELECT max(lngbookid) as lngbookid, max(strtitle) as strtitle, max(strauthor) as strauthor, max(strcoursecode) as strcoursecode, max(strisbn) as strisbn, max(strcontactname) as strcontactname, strcontactemail, max(curprice) as curprice, max(ysnsalerent) as ysnsalerent, max(dtmpostdate) as dtmpostdate, max(memcomments) as memcomments, max(school) as school, max(asin) as asin, max(bookimg) as bookimg, max(isbn10) as isbn10, max(isbn13) as isbn13, max(updated) as updated, max(datetime) as datetime, max(user_ip) as user_ip, max(nootherbooks) as nootherbooks FROM tblbooks WHERE strcoursecode LIKE '%$search%' GROUP BY strcontactemail ORDER BY datetime DESC LIMIT 50
 
 
  

編輯嗯，上面實際上太“假”了。 更好的方法是（提供列“lngbookid”是主鍵）：

SELECT a.lngbookid,
       a.strtitle,
       a.strauthor,
       a.strcoursecode,
       a.strisbn,
       a.strcontactname,
       a.strcontactemail,
       a.ontactemail,
       a.curprice,
       a.ysnsalerent,
       a.dtmpostdate,
       a.memcomments,
       a.school,
       a.asin,
       a.bookimg,
       a.isbn10,
       a.isbn13,
       a.updated,
       a.datetime,
       a.user_ip,
       a.nootherbooks
FROM   tblbooks AS a
       JOIN (SELECT strcontactemail,
                    Max(lngbookid) AS lngbookid
             FROM   tblbooks
             GROUP  BY strcontactemail) AS b
         ON ( a.strcontactemail = b.strcontactemail
              AND a.lngbookid = b.lngbookid )