java - DatabaseMetaData.getColumns() 中缺少列

Question

DatabaseMetaData.getColumns()的 Java 7 Javadoc说它返回一个包含 24 列的ResultSet，第一个名为TABLE_CAT，最后一个名为IS_GENERATEDCOLUMN。但是，我从 Oracle 收到的结果集只有 18 列。我用以下代码验证了它：

DatabaseMetaData databaseMetaData = connection.getMetaData();
ResultSet set = databaseMetaData.getColumns(catalogName, schemaPattern,
        tableNamePattern, columnNamePattern);
final ResultSetMetaData resultSetData = set.getMetaData();
final int columnCount = resultSetData.getColumnCount();

for (int columnIndex = 1; columnIndex <= columnCount; ++columnIndex) {
   final String columnName = resultSetData.getColumnName(columnIndex);
   System.out.printf("Column %d: %s%n", columnIndex, columnName);
}

上面的代码产生这个输出：

Column 1: TABLE_CAT
Column 2: TABLE_SCHEM
Column 3: TABLE_NAME
Column 4: COLUMN_NAME
Column 5: DATA_TYPE
Column 6: TYPE_NAME
Column 7: COLUMN_SIZE
Column 8: BUFFER_LENGTH
Column 9: DECIMAL_DIGITS
Column 10: NUM_PREC_RADIX
Column 11: NULLABLE
Column 12: REMARKS
Column 13: COLUMN_DEF
Column 14: SQL_DATA_TYPE
Column 15: SQL_DATETIME_SUB
Column 16: CHAR_OCTET_LENGTH
Column 17: ORDINAL_POSITION
Column 18: IS_NULLABLE

为什么我没有得到所有 24 列？我错过了什么？