java在jdbc元数据中获取columnCount=1

Question

表中的列数不断出错我做错了什么这是代码 这不对吗？我做错了什么？如何获得特定表的列数？：

public int getTableInfo(String tableName, String db, Boolean columnCount,
        Boolean rowCount) {

    TABLE = tableName;

    Connection getTableInfoConn = this.getConnect_to_DB(db);

    try {
        PreparedStatement prepStatement = getTableInfoConn
                .prepareStatement("SELECT COUNT(*) FROM `" + tableName
                        + "`");

        ResultSet res = prepStatement.executeQuery();

        if ((columnCount == false) && (rowCount == false)
                || (columnCount == null) && (rowCount == false)
                || (columnCount == false) && (rowCount == null)
                || (columnCount == null) && (rowCount == null)) {

            JOptionPane.showMessageDialog(null,
                    "uno de los booleanos debe ser TRUE", null,
                    JOptionPane.ERROR_MESSAGE, null);

        } else {

            if (columnCount == false && rowCount == true
                    || columnCount == null) {

                while (res.next()) {

                    resultMetaData = res.getInt(1);
                }
            } else if (columnCount == true && rowCount == false
                    || rowCount == null) {

                metaData = res.getMetaData();



                resultMetaData = metaData.getColumnCount();


            }

        }

    } catch (SQLException e) {

        JOptionPane.showMessageDialog(null, "Error in getTableInfo():" + e);
    }

    return resultMetaData;

}

主要方法是=

public static void main(String[] args) {

    ConectorBaseDatos dbconector = new ConectorBaseDatos();

    int numFilas = dbconector.getTableInfo("arbitros","fifa", false, true);

    System.out.println("Numero de filas de arbitros es : "+ numFilas);

    int numColumnas = dbconector.getTableInfo("arbitros", "fifa", true, false);

   System.out.println("numero de columnas es : " + numColumnas);
}

为什么columnCount = 1

Answer 1

您在这里发出的查询是：

select count(*) from arbitros;

结果将是一列、一行，只保留“arbitros”中的行数。该结果只有一列（名为“count（*）或类似内容）

如果需要arbitros中的列数，需要的查询是：

select * from arbitros;