JDBC PreparedStatement导致MySQL语法错误 [英] JDBC PreparedStatement results in MySQL syntax error

问题描述

我收到错误您的SQL语法出错了;请查看与您的MySQL服务器版本对应的手册，以便在第1行的''orderr'附近使用正确的语法 - 所以我假设错误是我使用了两个'，但在我的代码中我没有使用任何'。注意，该表实际上命名为orderr。

I am getting the error "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''orderr'' at line 1" - so I assume the error is that I have used two ' but in my code I have not used any '. NB the table is actually named orderr.

public void insertIntoDatabase(String table, Object... entries) {       // take a table and 
    Connection con = connect();                                         //add entries
    PreparedStatement preparedStatement = null;
    PreparedStatement preparedStatement2 = null;
    ResultSet rs = null;

    StringBuffer columnNames = new StringBuffer();
    StringBuffer sbEntries = new StringBuffer();
    for (int i = 0; i < entries.length; i++) {
        if (entries[i] instanceof Integer)
            sbEntries.append((Integer) entries[i]); 
        else if (entries[i] instanceof String)      
            sbEntries.append((String) entries[i]); 

        if (i != entries.length - 1)//if not last entry add 
            sbEntries.append(" ,"); // a ' ,'.
    }
    try {
        preparedStatement = con.prepareStatement("select * from ? ;");
        preparedStatement.setString(1, table);
        preparedStatement2 = con
                .prepareStatement("Insert into ?( ? ) values ( ? );");
        ResultSet resultSet = preparedStatement.executeQuery(); // get the
                                                                // number of
                                                                // columns
        ResultSetMetaData rsmd; // for the table
        rsmd = resultSet.getMetaData();
        int columnCount = rsmd.getColumnCount();
        for (int i = 1; i < columnCount + 1; i++) { // get column names, add to 
            columnNames.append(rsmd.getColumnName(i)); // to sb
            if (i != columnCount)
                columnNames.append(" ,");
        }
        columnCount = rsmd.getColumnCount();
        preparedStatement2.setString(1, table);                     
        preparedStatement2.setString(2, columnNames.toString());    //add sb's to statement
        preparedStatement2.setString(3, sbEntries.toString());
        preparedStatement2.executeUpdate();

    } catch (SQLException e) {
        System.out.println("2" + e.getMessage());
    }
    finally{
        try {
            if (rs != null) {
                rs.close();
            }
            if (preparedStatement != null) {
                preparedStatement.close();
            }
            if(preparedStatement2 != null){
                preparedStatement2.close();
            }
            if (con != null) {
                con.close();
            }

        } catch (SQLException e) {
            System.out.print("3" +e.getMessage());
        }

    }

}

推荐答案

在大多数数据库中，你不能参数化对象名称，比如表名，在MySQL中你理论上可以认为MySQL Connector / J默认不使用服务器端参数，而是重写它查询在发送到服务器之前。但是，该值将作为带引号的字符串插入，并且对象名称不能是带引号的字符串，因此它仍然无效。

In most databases you can't parametrize object names like table names, in MySQL you theoretically can as MySQL Connector/J by default doesn't use server side parameters, but instead it rewrites the query before sending it to the server. However the value will be inserted as a quoted string, and object names cannot be a quoted string, so it still won't work.

所以 INSERT INTO？或 SELECT ... FROM？将无效，因为它会产生 INSERT INTO'theTable'或 SELECT ... FROM'theTable'。

So INSERT INTO ? or SELECT ... FROM ? will not work, as it produces INSERT INTO 'theTable' or SELECT ... FROM 'theTable'.

对象名称必须是实际查询。不要使用参数。大多数其他数据库（或其驱动程序）会因为在此位置具有参数而抛出异常。

The object names need to be part of the actual query. Do not use parameters for them. Most other databases (or their drivers) would have thrown an exception for having a parameter in this position.

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