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我定义了以下 5 个表，其中在第一个 4 中插入了一些记录。这是使用启用了外键约束的 sqlite 3.7.1.7。

create table if not exists subject (id varchar(50) primary key,desc varchar(100));
insert into subject (id,desc) values ("subject1","test subject");

create table if not exists subjectlevel (id_subject_id varchar(50) references subject(id) on delete cascade, id integer not null, desc varchar(100) not null, questmcmaxselections integer not null, primary key (id_subject_id,id));

insert into subjectlevel (id_subject_id,id,desc,questmcmaxselections) values ("subject1",1,"test subject1 level 1",4);

insert into subjectlevel (id_subject_id,id,desc,questmcmaxselections) values ("subject1",2,"test subject1 level 2",4);

create table if not exists questmc (id integer primary key, text varchar(300) not null, includeallanswers int not null, subject_id varchar(50), subjectlevel_id integer, foreign key (subject_id, subjectlevel_id) references subjectlevel (id_subject_id,id) on delete cascade); 

insert into questmc (text,includeallanswers,subject_id,subjectlevel_id) values ("this is a _ question", 1, "subject1",1);

create table if not exists questmcselection (id integer primary key, text varchar(100) not null, subject_id varchar(50), subjectlevel_id integer, foreign key (subject_id, subjectlevel_id) references subjectlevel (id_subject_id,id) on delete cascade);

insert into questmcselection (text,subject_id,subjectlevel_id) values ("this is a solution","subject1",1);

create table if not exists questmc_questmcselection(id integer primary key, answer integer not null, questmc_id integer, questmcselection_id integer, subject_id varchar(50), subjectlevel_id integer, foreign key (questmc_id) references questmc(id) on delete cascade, foreign key (questmcselection_id) references questmcselection (id) on delete cascade, foreign key (subject_id,subjectlevel_id) references questmc (subject_id,subjectlevel_id) on delete cascade, foreign key (subject_id,subjectlevel_id) references questmcselection (subject_id,subjectlevel_id));

如果我尝试删除 subjectlevel 表中的第二条记录，只要定义了表 questmc_questmcselection，我就会收到外键不匹配错误。

sqlite> delete from subjectlevel where id=2;
Error: foreign key mismatch - "questmc_questmcselection" referencing "questmcselection"

questmc、questmcselection 和 questmc_questmcselection 没有应防止此删除的相关现有记录。知道为什么会发生此错误吗？

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2 回答 2

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subjectlevel此错误与此特定记录无关。

您的问题是您的表缺少所需的索引。这在之前没有报告，因为该DELETE语句是第一个需要 SQLite 检查数据库模式一致性的命令。

于 2013-06-09T20:19:43.453 回答
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根据 CL 的回答 -

sqlite> create table parent(a);
sqlite> create table child(a, FOREIGN KEY (a) REFERENCES parent(a));
sqlite> pragma foreign_keys = ON;
sqlite> insert into parent values(3);
sqlite> insert into child values (3);
Error: foreign key mismatch - "child" referencing "parent"
sqlite> create unique index p_a on parent(a);
sqlite> insert into child values (3);
sqlite> _

从文档中：

通常，外键约束的父键是父表的主键。如果 [not]，则父键列必须共同受 UNIQUE 约束或在父表的 CREATE TABLE 语句中具有 UNIQUE 索引 [使用] 排序规则序列。

即替代方案是：

sqlite> create table parent(a, b, UNIQUE (a, b));
sqlite> create table child (x, y, FOREIGN KEY (x, y) REFERENCES parent(a, b));

（这也突出了多列外键；它们也适用于索引......）

于 2014-07-03T16:11:43.843 回答