Question

当我向表中添加“ALTER TABLE”时，我在向数据库添加数据时遇到问题。我从我正在处理的网页获取信息，并将其写入将方法传输到数据库的java方法。如果我不使用两个ALTER TABLE语句，一切正常，但是一旦添加它们，信息将不再进入我的数据库。我究竟做错了什么？下面列出了CREATE TABLE和Java方法。希望有人可以帮助我！

CREATE TABLE role(
username VARCHAR(15) NOT NULL,
password VARCHAR(15) NOT NULL,
role VARCHAR(6) NOT NULL,
CONSTRAINT username_pk PRIMARY KEY (username)
);

CREATE TABLE customer(
orgnumber INTEGER NOT NULL,
companyname VARCHAR(20) NOT NULL,
contactperson VARCHAR(20),
streetname VARCHAR(30) NOT NULL,
zipcode INTEGER NOT NULL,
city VARCHAR(15) NOT NULL,
phone CHAR(12),
email VARCHAR(30) NOT NULL,
username VARCHAR(15),
CONSTRAINT orgnumber_pk PRIMARY KEY (orgnumber)
);

CREATE TABLE place(
zipcode INTEGER NOT NULL,
city VARCHAR(15),
streetname VARCHAR(30),
CONSTRAINT place_pk PRIMARY KEY (zipcode)
);

ALTER TABLE customer
    ADD CONSTRAINT role_fk1 FOREIGN KEY (username)
        REFERENCES role;

ALTER TABLE customer
    ADD CONSTRAINT place_fk1 FOREIGN KEY (zipcode)
        REFERENCES place;

Java方法：

public boolean regNewRegister(RegBean newRegister) {
    PreparedStatement sqlnewRegister = null;
    PreparedStatement sqlnewRole = null;
    PreparedStatement sqlnewPlace = null;
    String knd = "Customer";

    OpenConnection();
    boolean ok = false;
    try {
        /*
         * A transaction is started, uses lock.
         */
        if (connection == null) {
            System.out.println("Went well");
        }
        connection.setAutoCommit(false);

        sqlnewRegister = connection.prepareStatement("insert into customer (ORGNUMBER, CNAME, CONTACTP, STREETN, ZIPC, CITY, PHONE, EMAIL, USERNAME) values(?, ?, ?, ?, ?, ?, ?, ?, ?)");
        sqlnewRegister.setInt(1, newRegister.getOrgNumber());
        sqlnewRegister.setString(2, newRegister.getCompanyName());
        sqlnewRegister.setString(3, newRegister.getContactPerson());
        sqlnewRegister.setString(4, newRegister.getStreetName());
        sqlnewRegister.setInt(5, newRegister.getZipCode());
        sqlnewRegister.setString(6, newRegister.getCity());
        sqlnewRegister.setLong(7, newRegister.getPhone());
        sqlnewRegister.setString(8, newRegister.getEmail());
        sqlnewRegister.setString(9 newRegister.getUsername());

        sqlnewRole = connection.prepareStatement("insert into role (USERNAME, PASSWORD, ROLE) values (?, ?, ?)");
        sqlnewRole.setString(1, newRegister.getUsername());
        sqlnewRole.setString(2, newRegister.getPassword());
        sqlnewRole.setString(3, knd);

        sqlnewPlace = connection.prepareStatement("insert into place (ZIPC, CITY, STREETN) values (?, ?, ?)");

        sqlnewPlace.setInt(1, newRegister.getZipCode());
        sqlnewPlace.setString(2, newRegister.getCity());
        sqlnewPlace.setString(3, newRegister.getStreetName());

        sqlnewRegister.executeUpdate();
        sqlnewRole.executeUpdate();
        sqlnewPlace.executeUpdate();

        connection.commit();

        /*
         * Transaction ended
         */
        ok = true;

    } catch (SQLException e) {
        Cleaner.rollBack(connection);
        String sqlStatus = e.getSQLState().trim();
        String statusclass = sqlStatus.substring(0, 2);
        if (statusclass.equals("23")) { // Standard code for "integrity constraint violation"
            ok = false;  // This orgnumber is already registered
        } else {
            Cleaner.writeMessage(e, "WriteToDB");
        }
    } finally {
        Cleaner.settAutoCommit(connection);
        Cleaner.closeSentence(sqlnewRegister);
        Cleaner.closeSentence(sqlnewRole);
        Cleaner.closeSentence(sqlnewPlace);
    }
    closeConnection();
    return ok;
}

Answer 1

您必须先插入role和place，然后才能插入customer，否则将违反您的参照完整性。

两个ALTER TABLE语句表示customer.username必须具有相应的值role.username，而customer.zipcode必须指向有效的place.zipcode。

当您首先插入customer时，这些记录尚不存在。

编辑：

将executeUpdate的顺序更改为

    sqlnewRole.executeUpdate();
    sqlnewPlace.executeUpdate();
    sqlnewRegister.executeUpdate();

应该这样做。

EDIT2：

有一点需要注意的是，如果您有两个人使用相同的邮政编码，您的代码就会失败，因为如果您尝试添加两次，那么place的插入会违反主键...

如何在JavaDB和prepareStatement中创建表？

1 个答案: