MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails

Question

I have probed numerous questions and documentation on this error and cannot seem to find where I am going wrong. The error is on this line:

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: 
Cannot add or update a child row: a foreign key constraint fails (`flutweets`.`refs`,    
CONSTRAINT `refs_ibfk_1` FOREIGN KEY (`id`) REFERENCES `tweets` (`id`))

The database is MySQL, and I am using Workbench to inspect it; I also know that all the database engines are InnoDB and the Row Formats are Compact. I have three tables: tweets, hashtags, and references. Here is where I create the tables:

tweets Table

Statement stmt = null;
    try {
        stmt = connection.createStatement();
        stmt.executeUpdate("CREATE TABLE " + TWEETS_TABLE + "("
                + TWEETS_ID + " BIGINT NOT NULL AUTO_INCREMENT,"
                + TWEETS_TIME + " VARCHAR(255),"
                + TWEETS_USER + " VARCHAR(255),"
                + TWEETS_TEXT + " VARCHAR(255) NOT NULL,"
                + TWEETS_LOCATION + " VARCHAR(255),"
                + TWEETS_CITY + " VARCHAR(255),"
                + TWEETS_PROVINCE + " VARCHAR(255),"
                + TWEETS_COUNTRY + " VARCHAR(255),"
                + TWEETS_TIME_ZONE + " VARCHAR(255),"
                + TWEETS_LATITUDE + " DECIMAL(20,16),"
                + TWEETS_LONGITUDE + " DECIMAL(20,16),"
                + "PRIMARY KEY (" + TWEETS_ID + ")"
                + ")");
       . . .

hashtags Table

Statement stmt = null;
    try {
        stmt = connection.createStatement();
        stmt.executeUpdate("CREATE TABLE " + HASHTAG_TABLE + "("
                + HASHTAG_ID + " BIGINT NOT NULL AUTO_INCREMENT,"
                + HASHTAG_TEXT + " VARCHAR(255),"
                + TWEETS_ID + " BIGINT NOT NULL,"
                + "PRIMARY KEY (" + HASHTAG_ID + ")," 
                + "FOREIGN KEY (" + TWEETS_ID + ")"
                + "REFERENCES " + TWEETS_TABLE
                + "(" + TWEETS_ID + ")" 
                + ")");
      . . .

references Table

Statement stmt = null;
    try {
        stmt = connection.createStatement();
        stmt.executeUpdate("CREATE TABLE " + REF_TABLE + "("
                + REF_ID + " BIGINT NOT NULL AUTO_INCREMENT,"
                + REF_TEXT + " VARCHAR(255),"
                + TWEETS_ID + " BIGINT NOT NULL,"
                + "PRIMARY KEY (" + REF_ID + ")," 
                + "FOREIGN KEY (" + TWEETS_ID + ")"
                + "REFERENCES " + TWEETS_TABLE
                + "(" + TWEETS_ID + ")" 
                + ")");

Here are the statements I use to insert and the methods to insert them (I am using prepared statements):

/* INITIALIZE PREPARED STATEMENTS */

// Tweets
private static final String TWEETS_INSERT = "INSERT INTO " + TWEETS_TABLE
        + " (" + TWEETS_TIME + ", " + TWEETS_USER + ", " + TWEETS_TEXT + ", " + TWEETS_LOCATION + ", " + TWEETS_CITY + ", " + TWEETS_PROVINCE + ", "
        + TWEETS_COUNTRY + ", " + TWEETS_TIME_ZONE + ", " + TWEETS_LATITUDE + ", " + TWEETS_LONGITUDE + ")"
        + " VALUES(?,?,?,?,?,?,?,?,?,?)";
private PreparedStatement tweetsStatement;

// Hashtags
private static final String HASHTAGS_INSERT = "INSERT INTO " + HASHTAG_TABLE
        + " (" + HASHTAG_TEXT + ", " + TWEETS_ID + ")" + " VALUES(?,?)";
private PreparedStatement hashStatement;

// References
private static final String REF_INSERT = "INSERT INTO " + REF_TABLE
        + " (" + REF_TEXT + ", " + TWEETS_ID + ")" + " VALUES(?,?)";
private PreparedStatement refStatement;

public void insertHashtag(FluTweet tweet, int hashIndex, Integer tweetID) {

    // Pull all of the Hashtag's relevant elements.

    String hashText =  tweet.getHashtag(hashIndex);

    try {
        hashStatement.setString(1, hashText);
        hashStatement.setString(2, tweetID.toString());

        //INSERT HASHTAG INTO TABLE
        hashStatement.executeUpdate();

    } catch (SQLException e) {
        e.printStackTrace();
    }

}

public void insertReference(FluTweet tweet, int referenceIndex, Integer tweetID) {

    // Pull all of the Reference's relevant elements.

    String refText =  tweet.getReference(referenceIndex);

    try {
        refStatement.setString(1, refText);
        refStatement.setString(2, tweetID.toString());

        //INSERT REFERENCE INTO TABLE
        refStatement.executeUpdate();

    } catch (SQLException e) {
        e.printStackTrace();
    }

}

I have no idea why this is not working, any help would be much appreciated. Like I said, I have probed numerous other posts and cannot find relevant help.

Answer 1

Background

I found out the answer to my own question. It was never a problem with any of the actual database handling. It turns out, when I was passing the id to be used as the foreign id in hashtags and references, I was getting my id from a counter in the main class; where every new tweet had a number that went with each hashtag and reference for that tweet that would later be used as a foreign key. That foreign key would reference the primary key in the tweets table, which auto increments.

Here was the problem:

It turns out that MySQL is NOT zero-indexed when you auto-increment; where the first value is zero, then one, then two, etc. Instead, it starts at one. So when I tried to reference the primary key with the foreign key, the counter that started at zero for every tweet that I assigned (the foreign key) was being incorrectly matched to the auto incrementing tweet id in the tweets table (primary key).

Therefore, I was always off by one .

I hope this helps anyone that may have a similar issue.

Answer 2

如果未设置有效的子类对象主键值，则可以看到MySQLIntegrityConstraintViolationException。如果忽略子类对象的主键值，则基于hibernate pojo / hbm.xml文件一级缓存中设置的配置（会话）将其刷新到数据库中。