使用Java将数据插入mySQL数据库时出错

Question

各位晚安。 我有这些代码。 我只在这里复制了有问题的代码。

//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();
    }}

我看不到任何问题，但我有一个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

发生这种情况是因为你需要用引号括起不是整数的变量，否则数据库会将它们理解为列，只需在非整数列中添加引号，例如

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

我假设customer_cardno ， customer_phone ， debt是我tegers列，如果他们是nit只是环绕变量带引号

Answer 2

两件事情：

首先， SQL注入风险 。 我建议你看一下Prepared Statements： http ： //docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html

现在，如果您坚持构建类似的查询字符串，则应将要插入的String值括在引号中：

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"
 */