Cannot add or update a child row: a foreign key constraint fails (`myznt/answer`, CONSTRAINT `answer_ibfk_1` FOREIGN KEY (`qid`
MySQL5.0.15
一个问题表(question),一个回答表(answer)分别如下：
create table question
(
qid int auto_increment not null,
title VARCHAR(50),
content text,
itemid int,
subid int,
userid VARCHAR(50),
grade VARCHAR(50),
offerscore int,
status int,
questiontime datetime,
clickcount int,
acceptflag int,
commenflag int,
primary key (qid)
);
create table answer
(
aid int auto_increment not null,
quesans VARCHAR(50),
userid VARCHAR(50),
grade VARCHAR(50),
anstime datetime,
status int,
qid int,
primary key (aid) ,
foreign key (qid) references question(qid) on delete cascade
);
question表对应地hibernate3.1的映射文件为:Question.hbm.xml,内容如下:
<hibernate-mapping>
<class name="com.iwtxokhtd.vo.Question" table="question">
<id name="qid" type="java.lang.Integer">
<column name="qid" />
<generator class="native" />
</id>
<property name="title" type="java.lang.String">
<column name="title" length="50" />
</property>
<property name="content" type="java.lang.String">
<column name="content" length="65535" />
</property>
<property name="itemid" type="java.lang.Integer">
<column name="itemid" />
</property>
<property name="subid" type="java.lang.Integer">
<column name="subid" />
</property>
<property name="userid" type="java.lang.String">
<column name="userid" length="50" />
</property>
<property name="grade" type="java.lang.String">
<column name="grade" length="50" />
</property>
<property name="offerscore" type="java.lang.Integer">
<column name="offerscore" />
</property>
<property name="status" type="java.lang.Integer">
<column name="status" />
</property>
<property name="questiontime" type="java.util.Date">
<column name="questiontime" length="19" />
</property>
<property name="clickcount" type="java.lang.Integer">
<column name="clickcount" />
</property>
<property name="acceptflag" type="java.lang.Integer">
<column name="acceptflag" />
</property>
<property name="commenflag" type="java.lang.Integer">
<column name="commenflag" />
</property>
<set name="answers" inverse="true" table="answer">
<key>
<column name="qid" />
</key>
<one-to-many class="org.lxh.myzngt.vo.Answer" />
</set>
</class>
</hibernate-mapping>
answer表对应地hibernate3.1的映射文件为:Answer.hbm.xml,内容如下:
<hibernate-mapping>
<class name="com.iwtxokhtd.vo.Answer" table="answer">
<id name="aid" type="java.lang.Integer">
<column name="aid" />
<generator class="native" />
</id>
<many-to-one name="question" class="org.lxh.myzngt.vo.Question"
fetch="select">
<column name="qid" />
</many-to-one>
<property name="quesans" type="java.lang.String">
<column name="quesans" length="50" />
</property>
<property name="userid" type="java.lang.String">
<column name="userid" length="50" />
</property>
<property name="grade" type="java.lang.String">
<column name="grade" length="50" />
</property>
<property name="anstime" type="java.util.Date">
<column name="anstime" length="19" />
</property>
<property name="status" type="java.lang.Integer">
<column name="status" />
</property>
</class>
</hibernate-mapping>
[解决办法]
Cannot add or update a child row: a foreign key constraint fails (`myznt/answer`, CONSTRAINT `answer_ibfk_1` FOREIGN KEY (`qid`
你试图INSERT或UPDATE一个在question不存在的qid到answer表。
建议检查一下程序。
==== 思想重于技巧 ====
