Question

我写了这个Java类来打印DB2数据库的所有表，但问题是：它不打印所有列（我在代码中写了一些提示）。并且每次都打印以前的值！

public class automateExport {

static String value;

public static void main(String[] args) throws SQLException, ClassNotFoundException {

    String table_name;
    String column_name;
    String tableName = null;
    String columnType;
    int precision;
    StringBuilder sb = new StringBuilder(1024);
    Connection DB2 = getConnection();
    String sql = "SELECT TABSCHEMA,TABNAME,COLNAME,TYPENAME,LENGTH FROM SYSCAT.COLUMNS WHERE TABSCHEMA NOT LIKE 'SYS%' ";
    PreparedStatement mainStmt = DB2.prepareStatement(sql);
    ResultSet rs = mainStmt.executeQuery();
    ResultSetMetaData rsmd = rs.getMetaData();
    int columnCount = rsmd.getColumnCount();


        sb.append("create table").append(" ");
        rs.next();// if I Comment this line it does not work correctly.but this does not contain one column of table
        table_name = rs.getString(2);
        sb.append(table_name).append("(");
        String str1 = "ADMIN2";
        while (rs.next()) {
            table_name = rs.getString(2);
            if (table_name.equalsIgnoreCase(str1)) {


                column_name = rs.getString(3);
                columnType = rs.getString(4);
                sb.append(" ").append(column_name).append(" ").append(columnType);
                precision = rs.getInt(5);
                if (precision != 0) {
                    sb.append("( ").append(precision).append(" )");
                    sb.append(", ");

                }

            } else {
                sb.append(" ) ").append(";");
                System.out.println(sb.toString());

               str1 = str1.replaceAll(str1, table_name);
               sb.append("create table").append(" ");
               sb.append(table_name).append("(");
               //rs.previous();
            }

       // sb.append(" ) ").append(";");
        //System.out.println(sb.toString());

    }
    Class.forName("oracle.jdbc.driver.OracleDriver");
    Connection codal = DriverManager.getConnection("jdbc:oracle:thin:@192.168.01.53:1521:orcl", "NAVID",
            "oracle");

    /* String sql2 = sb.toString();
     PreparedStatement m = DB2.prepareStatement(sql2);
     m.executeQuery();*/
}

private static Connection getConnection() throws ClassNotFoundException, SQLException {
    Class.forName("COM.ibm.db2os390.sqlj.jdbc.DB2SQLJDriver");
    Connection connection
            = DriverManager.getConnection("jdbc:db2://localhost:50000/navid", "navid", "oracle");
    return connection;
   }
 }

输出是这样的：

run:

create table ADMIN2( NAME VARCHAR( 30 ),  ROLE VARCHAR( 50 ),  ) ;

create table ADMIN2( NAME VARCHAR( 30 ),  ROLE VARCHAR( 50 ),  ) ;create table DOCUMENT( ID DECIMAL( 10 ),  NAME VARCHAR( 50 ),  ) ;

BUILD SUCCESSFUL (total time: 1 second)

Answer 1

您必须在while循环中初始化StringBuilder：

...
       while (rs.next()) {
          StringBuilder sb = new StringBuilder(1024);
...

Answer 2

您可以尝试使用此代码，认为它可能有所帮助。因为在大多数情况下rs.next在没有while循环的情况下不起作用

    sb.append("create table").append(" ");
    while(rs.next())
    {
    table_name = rs.getString(2);
    sb.append(table_name).append("(");
    }

Java类，用于从数据库中检索所有表

2 个答案: