Question

我有一个应用程序，如果在Microsoft Access数据库中退出，我需要删除表。我看到了代码here。我要删除的表名是 data_table ，访问数据库文件名是 local_entry 所以我需要更改代码，以便它适用于我的应用程序。

public void testDropTable () throws SQLException{
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    Connection con = DriverManager.getConnection("jdbc:odbc:MsAccessDSN");
    Statement stmt = con.createStatement();
    ResultSet checkTable = con.getMetaData().getTables(null, null, "POI", null);
    String tableName = null;
    while (checkTable.next())
    {
        System.out.println("In here");
        tableName = checkTable.getString("TABLE_NAME");
        System.out.println(tableName);
    }
    if (tableName != null){
        try {
            String dropTable = "DROP TABLE ";
            String[] tables = DB_TABLE;
            for (int i = 0; i < tables.length; i++){
                String stringCode = new String();
                stringCode = stringCode + tables[i];
                System.out.println(dropTable + tables[i]);

                // Drop each table in the array.
                int temp = stmt.executeUpdate(dropTable + tables[i]);
            }
        }
        catch (Exception e) {
            System.err.println("Exception in testDropTable (): \n"
                    + "Drop Table testDropTable threw an exception: " +(e.getMessage()));
        }
    }
    else{
        con.close();
    }
}

我想我需要改变这两行：

String dropTable = "DROP TABLE ";
String[] tables = DB_TABLE;

我可以将 DROP TABLE 更改为 data_table 以及第二行。这是什么 DB_TABLE 我通过这种方式更改了整个代码，但直到出现问题：

public void testDropTable () throws SQLException{
    try {
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    } catch (ClassNotFoundException e1) {
        e1.printStackTrace();
    }
    Connection con = DriverManager.getConnection("jdbc:odbc:MsAccessDSN");
    Statement stmt = con.createStatement();
    ResultSet checkTable = con.getMetaData().getTables(null, null, "POI", null);
    String tableName = null;
    while (checkTable.next())
    {
        System.out.println("In here");
        tableName = checkTable.getString("data_table");
        System.out.println(tableName);
    }
    if (tableName != null){
        try {
            String dropTable = "DROP TABLE ";
            String[] tables = {"data_table"};
            for (int i = 0; i < tables.length; i++){
                String stringCode = new String();
                stringCode = stringCode + tables[i];
                System.out.println(dropTable + tables[i]);

                // Drop each table in the array.
                int temp = stmt.executeUpdate(dropTable + tables[i]);
            }
        }
        catch (Exception e) {
            System.err.println("Exception in testDropTable (): \n"
                    + "Drop Table testDropTable threw an exception: " +(e.getMessage()));
        }
    }
    else{
        con.close();
    }
}

Answer 1

删除表格表名称; 是删除数据库中表格的命令。尝试将 DB_TABLE 替换为 data_table 。

String dropTable = "DROP TABLE ";
String[] tables = data_table;

试试这个

    public void testDropTable () throws SQLException{
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    Connection con = DriverManager.getConnection("jdbc:odbc:MsAccessDSN");
    Statement stmt = con.createStatement();
    ResultSet checkTable = con.getMetaData().getTables(null, null, "POI", null);
    String tableName = null;
    while (checkTable.next())
    {
        System.out.println("In here");
        tableName = checkTable.getString("data_table");
        System.out.println(tableName);
    }
    if (tableName != null){
        try {
            String dropTable = "DROP TABLE ";
            String[] tables = tableName;
            for (int i = 0; i < tables.length; i++){
                String stringCode = new String();
                stringCode = stringCode + tables[i];
                System.out.println(dropTable + tables[i]);

                // Drop each table in the array.
                int temp = stmt.executeUpdate(dropTable + tables[i]);
            }
        }
        catch (Exception e) {
            System.err.println("Exception in testDropTable (): \n"
                    + "Drop Table testDropTable threw an exception: " +(e.getMessage()));
        }
    }
    else{
        con.close();
    }
}

Answer 2

试试这段代码

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection con = DriverManager.getConnection("jdbc:odbc:MsAccessDSN");
Statement stmt = con.createStatement();
// Specify the type of object; in this case we want tables
String[] types = {"TABLE"};
ResultSet checkTable = con.getMetaData().getTables(null, null, "%", types);
String tableName = null;

while (checkTable.next())
{
    System.out.println("In here");
    tableName = checkTable.getString(3)
    System.out.println(tableName);

    // check if the table 'data_table' exist in your database
    if (tableName.equals("data_table"){    
        try {
            //drop the table if present  
            int temp = stmt.executeUpdate("DROP TABLE " + tableName);
            break;
        }
        catch (Exception e) {
            System.err.println("Exception in testDropTable (): \n"
                + "Drop Table testDropTable threw an exception: " +(e.getMessage()));
        }
    }    
}
con.close;

有关详细信息，请访问Metadata

Answer 3

对于对此问题感兴趣的任何人，我都删除了已接受答案中的while循环语句，并将代码简化为：

public void testDropTable() throws SQLException, ClassNotFoundException {
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        Connection con = DriverManager.getConnection("jdbc:odbc:MsAccessDSN");
        Statement stmt = con.createStatement();
        String[] tables = {"data_table"};
        for (String table : tables) {
            try {
                stmt.executeUpdate("DROP TABLE " + table);
            } catch (SQLException e) {
                System.err.println("Exception in testDropTable (): \n"
                    + "Drop Table testDropTable threw an exception: " +(e.getMessage()));
            }
        }
        con.close();
    }

删除表（如果存在于Microsoft Access中）

3 个答案: