mysql查询帮助从表中删除条目

Question

我有2个msql表（记录和播放器）whitch包含以下字段：

records = Id  PlayerId  Score  Date  Checkpoints  

players = Id Login Game NickName Nation UpdatedAt Wins TimePlayed TeamName 

我从播放器db中删除了几个，我将从记录表中删除此值。

db中的Id值相同。

我使用了这个命令：

DELETE FROM `players` WHERE `players`.`Id` = 27;

但删除后，Id` = 27仍然存在于记录表中。

所以现在玩家表中没有id 27但是我会从记录中删除它。 我还有120个参赛作品:(

Answer 1

如果您希望在从records删除时自动从players表中删除相关行，则需要将PlayerId声明为ON DELETE CASCADE的外键选项。

ALTER TABLE records ADD CONSTRAINT fk_playerid FOREIGN KEY (PlayerId) REFERENCES players (id) ON DELETE CASCADE;

这只有在您使用InnoDB时才有效;在MyISAM中忽略外键。

如果您不能使用外键，则可以在删除时加入表格：

DELETE p, r FROM players AS p
LEFT JOIN records AS r ON p.id = r.PlayerId
WHERE p.id = 27;

这需要使用LEFT JOIN;如果您使用INNER JOIN，则不会删除没有相关记录的玩家。

Answer 2

使用内部联接

尝试此操作

DELETE records, players  FROM records  INNER JOIN players  
WHERE records.Id= players.Id and records.Id = '27'

这应该删除表格

如果您在一个表中不存在记录：

 DELETE records, players  FROM records  INNER JOIN players  
 WHERE records.Id != players.Id 

Answer 3

DELETE FROM records WHERE NOT PlayerId IN (SELECT Id FROM players)

这将删除所有不属于玩家的记录。