使用Java将数据插入mySQL数据库时出错

Question

Good night everyone. I have these codes. I only copied here the codes which have the problem.

//This is my main method. I called my Database.class, made the connection and called the insertnewcustomer method.

public static void main(String[] args) {
    Database db = new Database();
    db.connectDB();
    db.insertNewCustomer(86754312, "arda", "zenci", 55418, 400);
.................//

//and here is my insertNewCustomer method which is inside the Database.class

public void insertNewCustomer(int num, String name, String surname, int phone, int debt){
    try {
        statement.executeUpdate("INSERT INTO Customer(customer_cardno, customer_name, customer_sirname, customer_phone, debt) VALUES(" + num + ", " + name  + ", " + surname + ", " + phone + ", " + debt + ")");
    } catch (SQLException e) {
        e.printStackTrace();
    }}

I cannot see any problems but I have a MySQLSyntaxErrorException

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'arda' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4187)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4119)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2570)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2731)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2809)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1811)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1725)
at Database.insertNewCustomer(Database.java:39)
at mainFrame.main(mainFrame.java:50)

Answer 1

This is happening because you need to surround variables which are not integers with quotes, otherwise database would understand them as column, simply add quotes in not integers column, such as

statement.executeUpdate("INSERT INTO Customer(customer_cardno, customer_name, customer_sirname, customer_phone, debt) VALUES(" + num + ", '" + name  + "', '" + surname + "', " + phone + ", " + debt + ")");

I assumed customer_cardno , customer_phone , debt being i tegers columns, if they are nit just surround variabkes with quotes

Answer 2

Two things:

First, SQL Injection risk . I suggest you take a look on Prepared Statements: http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html

Now, if you insist in building the query string like that, you should enclose the String values you are inserting in quotes:

statement.executeUpdate("INSERT INTO Customer " + 
    (customer_cardno, customer_name, customer_sirname, customer_phone, debt) " + 
    VALUES(" + num + ", '" + name  + "', '" + surname + "', '" + phone + "', " + debt + ")");
/*
 * Notice the single quotes arround "name", "surname" and "phone"
 */