選擇NULL列

Question

我寫了一個查詢，它選擇的列有時是NULL。

$q = "SELECT g.id AS gameid,g.home_user, g.home_user2, g.away_user, g.away_user2, g.home_score, g.away_score, g.date_confirmed, g.type, 
      h1.username AS home_username, h2.username AS home_username2, a1.username AS away_username2, a2.username AS away_username2 
      FROM ".TBL_FOOT_GAMES." g 
      INNER JOIN ".TBL_USERS." h1 ON h1.id = g.home_user 
      INNER JOIN ".TBL_USERS." h2 ON h2.id = g.home_user2 
      INNER JOIN ".TBL_USERS." a1 ON a1.id = g.away_user 
      INNER JOIN ".TBL_USERS." a2 ON a2.id = g.away_user2 
      WHERE g.status = '$status' 
      ORDER BY g.date_confirmed DESC LIMIT 25"; 

列

home_user2和away_user2

可以是NULL有時。顯然這似乎阻止了查詢顯示任何返回的數據。 當我從查詢中刪除這些列時，我得到了回報。 包括他們不是拋出一個錯誤，只是簡單的是不選擇任何行。

我該如何解決這個問題？

Answer 1

您將需要使用left join，而不是這些列上的內部聯接。

$q = "SELECT g.id AS gameid,g.home_user, g.home_user2, g.away_user, g.away_user2, g.home_score, g.away_score, g.date_confirmed, g.type, 
      h1.username AS home_username, h2.username AS home_username2, a1.username AS away_username2, a2.username AS away_username2 
      FROM ".TBL_FOOT_GAMES." g 
      INNER JOIN ".TBL_USERS." h1 ON h1.id = g.home_user 
      LEFT JOIN ".TBL_USERS." h2 ON h2.id = g.home_user2 
      INNER JOIN ".TBL_USERS." a1 ON a1.id = g.away_user 
      LEFT JOIN ".TBL_USERS." a2 ON a2.id = g.away_user2 
      WHERE g.status = '$status' 
      ORDER BY g.date_confirmed DESC LIMIT 25";