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我正在使用包含 XMLType 列的 Oracle 表。我发现它是虚拟的，但是当我创建表时，该列没有标记为“虚拟”属性。所以我的问题是为什么这个列在 ALL_TAB_COLS 中是虚拟的，它是否真的是虚拟的？创建表语句：

CREATE TABLE ALL_TYPES
(
  MAXVARCHAR2     VARCHAR2(4000),
  MINVARCHAR2     VARCHAR2(1),
  MAXVARCHAR      VARCHAR2(4000),
  MINVARCHAR      VARCHAR2(1),
  MAXCHAR         CHAR(2000),
  MINCHAR         CHAR,
  MAXNCHAR        NCHAR(1000),
  MINNCHAR        NCHAR(1),
  MAXNUMBER       NUMBER(*, 127),
  NORMALNUMBER    NUMBER,
  MINNUMBER       NUMBER(1, -83),
  BINARYFLOAT     BINARY_FLOAT,
  BINARYDOUBLE    BINARY_FLOAT,
  LONG_           LONG,
  DATE_           DATE,
  MINTIMESTAMP    TIMESTAMP(0),
  TIMESTAMP       TIMESTAMP(6),
  MAXTIMESTAMP    TIMESTAMP(9),
  MINTIMESTAMP_TZ TIMESTAMP(0) WITH TIME ZONE,
  TIMESTAMP_TZ    TIMESTAMP(6) WITH TIME ZONE,
  MAXTIMESTAMP_TZ TIMESTAMP(9) WITH TIME ZONE,
  MINITERVAL_YEAR INTERVAL YEAR(0) TO MONTH,
  ITERVAL_YEAR    INTERVAL YEAR(2) TO MONTH,
  MAXITERVAL_YEAR INTERVAL YEAR(9) TO MONTH,
  MININTERVAL_DAY INTERVAL DAY(0) TO SECOND(0),
  INTERVAL_DAY    INTERVAL DAY(2) TO SECOND(6),
  MAXINTERVAL_DAY INTERVAL DAY(9) TO SECOND(9),
  MAXRAW          RAW(2000),
  MINRAW          RAW(1),
  ROWID_          ROWID,
  UROWID_         UROWID,
  CLOB_           CLOB,
  NCLOB_          NCLOB,
  BLOB_           BLOB,
  BFILE_          BFILE,
  XMLTYPE_        XMLTYPE
)
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