Question

我有两个数据库表。

tblTeams：PK TeamID，TeamName
tblMatches：PK match id，FK HomeTeam，FK AwayTeam,Score。

我正在使用SQL Server 2008，我通过向导从.csv文件导入行。 csv中的列为hometeam，awayteam，score。因此，在插入tblMatches之前，我想要一个触发器来查找团队的FK并在tblMatches中插入外键而不是名称。

请提供任何帮助。

CREATE TRIGGER tblmatches_BeforeInsert
ON tblmatches
BEFORE INSERT
AS 
BEGIN
    INSERT  tblmatches
    SELECT  teamName
    FROM    tblmatches
    WHERE   tblTeams.id = ?i dont know here what to insert? 
END

Answer 1

AFAIK，对于要在tblMatches上调用的触发器，您需要为该表中的所有列提供值，并且仅为该表中的列提供值，这意味着，您无法将团队名称传递给触发器，以便它可以用于解析团队ID。

如果我这样做，我只会创建一个表来按原样插入原始数据，让导入向导将记录写入此表，在此表上定义一个触发器，将记录插入到两个派生表中即可。 tblTeams，tblMatches。（SQL Server Triggers）

我尝试编写一个（没有机会验证，因为我没有SQL服务器）

CREATE TRIGGER teams.process ON teams
AFTER INSERT
AS
BEGIN
    DECLARE @homeTeamId INT
    DECLARE @awayTeamId INT
    DECLARE @maxTeamId INT
    DECLARE @matchId INT

    SELECT @maxTeamId = 0
    SELECT @maxTeamId = ISNULL(MAX(teamId), 0) from tblTeams

    --- Check if home team has already been inserted into the table.
    SELECT @homeTeamId = -1
    SELECT 
        @homeTeamId = teamId 
    FROM 
        tblTeams t
        JOIN inserted i
        ON t.teamName = i.hometeam
    IF (@homeTeamId = -1) 
    BEGIN
        SELECT @homeTeamId = @maxTeamId + 1
        SELECT @maxTeamId = @maxTeamId + 1
        INSERT INTO tblTeams SELECT @homeTeamId, i.hometeam FROM inserted i
    END

    --- Check if away team has already been inserted into the table.
    SELECT @awayTeamId = -1
    SELECT 
        @awayTeamId = teamId 
    FROM 
        tblTeams t
        JOIN inserted i
        ON t.teamName = i.awayteam
    IF (@awayTeamId = -1) 
    BEGIN
        SELECT @awayTeamId = @maxTeamId + 1
        SELECT @maxTeamId = @maxTeamId + 1
        INSERT INTO tblTeams SELECT @awayTeamId, i.awayteam FROM inserted i
    END

    -- insert a record into the matches table with the home team ID and away team ID.
    SELECT @matchId = 0
    SELECT @matchId = ISNULL(MAX(MatchId), 0) FROM tblMatches
    INSERT INTO tblMatches 
    SELECT @matchId + 1, @homeTeamId, @awayTeamId, i.score 
    FROM inserted i
END

Answer 2

如果你想在表中使用不同的表示，那么你可能必须实现一个视图，并通过它来执行插入，而不是基表。

类似的东西：

CREATE TABLE realMatches (
    MatchID int IDENTITY(1,1) not null, /* Identity? */
    HomeTeamID int not null,
    AwayTeamID int not null,
    Score int not null, /* int? */
    constraint PK_realMatches PRIMARY KEY (MatchID),
    constraint FK_Matches_HomeTeams (HomeTeamID) references tblTeams (TeamID),
    constraint FK_Matches_AwayTeams (AwayTeamID) references tblTeams (TeamID)
)
GO
CREATE VIEW tblMatches
AS
    SELECT
        MatchID,
        ht.TeamName as HomeTeam,
        at.TeamName as AwayTeam,
        Score
    FROM
        realMatches m
           inner join
        tblTeams ht
           on
               m.HomeTeamID = ht.TeamID
           inner join
        tblTeams at
           on
               m.AwayTeamID = at.TeamID
GO
CREATE TRIGGER T_Matches ON tblMatches
INSTEAD OF INSERT
AS
     SET NOCOUNT ON

     INSERT INTO realMatches (HomeTeamID,AwayTeamID,Score)
     SELECT ht.TeamID,at.TeamID,i.Score
     FROM
        inserted i
           inner join
        tblTeam ht
           on
              i.HomeTeam = ht.TeamName
           inner join
        tblTeam at
           on
              i.AwayTeam = at.TeamName

您现在可以（假设“{1}}中存在”A Team“和”Team America“）：

tblTeams

当然，这还没有（还）处理任何试图更改匹配表中的团队的更新，以及如果{{{ 1}}，但你还没有问过这些。

sql Trigger：在插入之前从另一个表中选择FK

2 个答案: