Question

我有这样的表结构：

PrimaryTable - ＆gt; p_id 此处p_id是主要

SecondoryTable - ＆gt; s_id p_id 此处p_id是外键

ThirdTable - ＆gt; t_id s_id 此处s_id是外键

FourthTable - ＆gt; f_id t_id 此处t_id是外键

因此，我要从p_id删除我的PrimaryTable之一并希望其SecondoryTable数据也应删除，ThirdTable数据应删除{SecondoryTable应参考FourthTable

删除1}}和ThirdTable数据

我知道我可以从下到上编写Delete查询，但是如何处理这么多级别？

我发现了这个但不确定如何：https://stackoverflow.com/a/9847308/1182021

因为它的四级层次结构我很困惑。

EDIT1：

如果要在删除Primary

时删除Child该怎么办？

请建议。

Answer 1

根据OP的请求，这是当用户想要从子表中删除行时从父表中删除行的情况的答案。删除父项时递归删除所有子项的情况正在使用MySQL ON DELETE CASCADE选项。

4个表格是table1，table2，table3＆amp;表4

如果用户想要删除table2中的行以及table1中的相应行（table2的父级），那么在PHP中：

// t2_delete_row_id is the id of the table 2 row to be deleted
// get the the parent of table2
$sql_get_parent = "select p_id from table2 where s_id = 't2_delete_row_id '";
// execute this query using MySQLi/PDO to get id of the parent row to be deleted
// assuming that id is t1_parent_row_id
// now delete the row from table 2:
// note that because of the foreign key constraints, 
// corresponding rows from table3 and table4 would also be deleted
$sql_delete_child = "delete from table2 where s_id = 't2_delete_row_id'";
if (mysqli_query($sql_delete_child)){
    // delete the parent row
    $sql_delete_parent = "delete from table1 where p_id = 't1_parent_row_id'";
}

可以扩展此逻辑，以便在删除table3行时，也会删除相应的父（table2）和“grand-parent”（table1）行。这种情况可能需要一些递归。当然，由于外键约束，这当然会删除table4中的子行。

Answer 2

如果您无法使用FOREIGN KEYS（即使用MyISAM表），我会为此创建一个TRIGGER。下面第一个示例...您将需要为每个级联的表创建一个。

DELIMITER //
CREATE TRIGGER `pDeleteTrigger` BEFORE DELETE ON `PrimaryTable`
 FOR EACH ROW BEGIN
    DELETE FROM `SecondoryTable` WHERE NEW.`p_id` = `SecondoryTable`.`p_id`
END
//
DELIMITER ;

Answer 3

我脑子里有两种方法（如果你的语言是Tsql）

1.-存储程序

这个想法是有一个程序“spDelete_PrimaryTable”，这样你就可以通过在tsql中写一些东西来删除四个表中的寄存器，如：

 exec spDelete_PrimaryTable
       @p_id= 25 /* (25 or watever p_id of primary table you want to delete)*/

（是的，你可以从你想要的vb.net或watever中调用它。）

代码如下：

use [your_database]

CREATE PROCEDURE [dbo].[spDelete_PrimaryTable]
    @p_id nvarchar(MAX)
AS 
 begin  
    SET NOCOUNT ON;

delete from FourthTable where t_id in (
    select ThirdTable.t_id 
    from ThirdTable inner join SecondoryTable on ThirdTable.s_id = SecondoryTable.s_id
    where SecondoryTable.p_id = @p_id
)
go

delete from ThirdTable where s_id in (
    select SecondoryTable.s_id 
    where SecondoryTable.p_id = @p_id
)
go

    /*Lol, I forgot to eliminate from the "SecondoryTable" */
    delete from SecondoryTable.s_id 
    where SecondoryTable.p_id = @p_id

go

delete from PrimaryTable where p_id = @p_id
go

 END


GO

2.-触发

似乎“克里斯托弗·莫里西”已经发布了我正在编辑这个答案的XP

删除主要删除所有外键数据，反之亦然

3 个答案: