SQL語句中被零除如何避免特定記錄如果它返回被零除

Question

我試圖發表一個聲明，讓球員進球得分，然后按比賽進行划分。 如果玩家已經玩了 0 場比賽，就會出現 0 分局。 我如何“跳過”或忽略這一點並為每場比賽的目標顯示 N/A？ 這是我目前擁有的：

SELECT PlayerName, PlayerSurname, GamesPlayed, GoalsScored, ROUND(GoalsScored/GamesPlayed ,2) AS GoalsPerGame
FROM tblPlayers , tblStatistics 
WHERE tblPlayers.PlayerID = tblStatistics.PlayerID 
ORDER BY GoalsScored DESC

我在 delphi 10.3 中這樣做，所以表的連接是在 where 語句中完成的，但這不會影響一般問題。 如果我為一張唱片做這件事，我會做的

if tblStatistics['GamesPlayed'] = 0 then
begin
qryStatsStatic.SQL.Clear;
qryStatsStatic.SQL.Add('
SELECT PlayerName, PlayerSurname, GamesPlayed, GoalsScored, "N/A" AS GoalsPerGame
FROM tblPlayers , tblStatistics 
WHERE tblPlayers.PlayerID = tblStatistics.PlayerID 
ORDER BY GoalsScored DESC');
qryStatistics.open;
end;

但我的問題是多條記錄。

Answer 1

您可以使用大多數流行的 DBMS 中存在的簡短nullif函數：

select
  ...,
  ROUND(GamesPlayed/nullif(GoalsScored, 0) ,2) as GoalsPerGame
...

Answer 2

SQL 有 CASE 語句，它只在找到匹配項之前執行。

CASE WHEN COALESCE(GamesPlayed,0) = 0 THEN 0
     ELSE ROUND(GoalsScored/GamesPlayed,2) 
END AS GoalsPerGame

每場比賽的目標也將是目標/游戲。

Answer 3

嘗試 SQL 聯合：

SELECT PlayerName, PlayerSurname, GamesPlayed, GoalsScored, 
       ROUND(GamesPlayed/GoalsScored ,2) AS GoalsPerGame
FROM tblPlayers , tblStatistics 
WHERE tblPlayers.PlayerID = tblStatistics.PlayerID
  AND GoalsScored <> 0
UNION
SELECT PlayerName, PlayerSurname, GamesPlayed, GoalsScored, 0
FROM tblPlayers , tblStatistics 
WHERE tblPlayers.PlayerID = tblStatistics.PlayerID
  AND GoalsScored = 0
ORDER BY GoalsScored DESC