oracle所有表的基本信息

原文：http://docs.oracle.com/cd/B19306_01/server.102/b14237/statviews_2094.htm

ALL_TAB_COLUMNS

ALL_TAB_COLUMNS describes the columns of the tables, views, and clusters accessible to the current user. To gather statistics for this view, use theANALYZE SQL statement or the DBMS_STATS package.

Related Views

• DBA_TAB_COLUMNS describes the columns of all tables, views, and clusters in the database.

• USER_TAB_COLUMNS describes the columns of the tables, views, and clusters owned by the current user. This view does not display the OWNERcolumn.

Column	Datatype	NULL	Description
OWNER	VARCHAR2(30)	NOT NULL	Owner of the table, view, or cluster
TABLE_NAME	VARCHAR2(30)	NOT NULL	Name of the table, view, or cluster
COLUMN_NAME	VARCHAR2(30)	NOT NULL	Column name
DATA_TYPE	VARCHAR2(106)		Datatype of the column
DATA_TYPE_MOD	VARCHAR2(3)		Datatype modifier of the column
DATA_TYPE_OWNER	VARCHAR2(30)		Owner of the datatype of the column
DATA_LENGTH	NUMBER	NOT NULL	Length of the column (in bytes)
DATA_PRECISION	NUMBER		Decimal precision for NUMBERdatatype; binary precision forFLOAT datatype, null for all other datatypes
DATA_SCALE	NUMBER		Digits to right of decimal point in a number
NULLABLE	VARCHAR2(1)		Specifies whether a column allows NULLs. Value is N if there is a NOT NULL constraint on the column or if the column is part of a PRIMARY KEY. The constraint should be in an ENABLE VALIDATE state.
COLUMN_ID	NUMBER		Sequence number of the column as created
DEFAULT_LENGTH	NUMBER		Length of default value for the column
DATA_DEFAULT	LONG		Default value for the column
NUM_DISTINCT	NUMBER		Number of distinct values in the columnFoot 1
LOW_VALUE	RAW(32)		Low value in the columnFootref 1
HIGH_VALUE	RAW(32)		High value in the columnFootref 1
DENSITY	NUMBER		Density of the columnFootref 1
NUM_NULLS	NUMBER		Number of nulls in the column
NUM_BUCKETS	NUMBER		Number of buckets in the histogram for the column Note: The number of buckets in a histogram is specified in the SIZEparameter of the SQL statementANALYZE. However, the Oracle Database does not create a histogram with more buckets than the number of rows in the sample. Also, if the sample contains any values that are very repetitious, the Oracle Database creates the specified number of buckets, but the value indicated by this column may be smaller because of an internal compression algorithm.
LAST_ANALYZED	DATE		Date on which this column was most recently analyzed
SAMPLE_SIZE	NUMBER		Sample size used in analyzing this column
CHARACTER_SET_NAME	VARCHAR2(44)		Name of the character set:CHAR_CS or NCHAR_CS
CHAR_COL_DECL_LENGTH	NUMBER		Length
GLOBAL_STATS	VARCHAR2(3)		For partitioned tables, indicates whether column statistics were collected for the table as a whole (YES) or were estimated from statistics on underlying partitions and subpartitions (NO)
USER_STATS	VARCHAR2(3)		Indicates whether statistics were entered directly by the user (YES) or not (NO)
AVG_COL_LEN	NUMBER		Average length of the column (in bytes)
CHAR_LENGTH	NUMBER		Displays the length of the column in characters. This value only applies to the following datatypes: CHAR VARCHAR2 NCHAR NVARCHAR
CHAR_USED	VARCHAR2(1)		B | C. B indicates that the column uses BYTE length semantics. Cindicates that the column usesCHAR length semantics. NULLindicates the datatype is not any of the following: CHAR VARCHAR2 NCHAR NVARCHAR2
V80_FMT_IMAGE	VARCHAR2(3)		Indicates whether the column data is in release 8.0 image format (YES) or not (NO)
DATA_UPGRADED	VARCHAR2(3)		Indicates whether the column data has been upgraded to the latest type version format (YES) or not (NO)
HISTOGRAM	VARCHAR2(15)		Indicates existence/type of histogram: NONE FREQUENCY HEIGHT BALANCED