Search notes:

Columns of and differences between DBA_TAB_COLUMNS and DBA_TAB_COLS

dba_tab_columns is related to dba_tab_cols, but shows only columns that are not system generated, i.e the definition of the view dba_tab_columns excludes user generated columns: 
create view DBA_TAB_COLUMNS as
select
 …
from
  DBA_TAB_COLS
where
  USER_GENERATED = 'YES';

with
  c1 as (select * /* column_name, data_type, data_length, data_precision */ from dba_tab_cols where owner = 'SYS' and table_name = 'DBA_TAB_COLS'   ),
  c2 as (select * /* column_name, data_type, data_length, data_precision */ from dba_tab_columns where owner = 'SYS' and table_name = 'DBA_TAB_COLUMNS')
select
  nvl(c1.column_name, c2.column_name) column_name,
  nvl(case when c1.column_name is null and c2.column_name is not null then 'only in dba_tab_columns' end,
 case when c2.column_name is null and c1.column_name is not null then 'only in dba_tab_cols'    end
  )  where_
-- c1.data_type  , c2.data_type,
-- c1.column_id  , c2.column_id
from
  c1 full outer join
  c2 on c1.column_name = c2.column_name
order by
  c1.column_id,
  c2.column_id;
OWNER
TABLE_NAME
COLUMN_NAME
DATA_TYPE The column's data type
DATA_TYPE_MOD
DATA_TYPE_OWNER
DATA_LENGTH
DATA_PRECISION
DATA_SCALE Number of digits to the right of the decimal point.
NULLABLE
COLUMN_ID
DEFAULT_LENGTH
DATA_DEFAULT If VIRTUAL_COLUMN = 'YES', this column stores the expression for virtual columns with which a column value is calculated at query time or, if IDENTITY_COLUMN = 'YES', the nextval sequence expression which is used at insert time of an identity column.
NUM_DISTINCT
LOW_VALUE, HIGH_VALUE The lowest/highest value in the column found when the column statistics were last gathered. Use on of the dbms_stats.convert_raw_to_<datatype> functions to convert the raw value stored in these column to more readable values.
DENSITY
NUM_NULLS
NUM_BUCKETS
LAST_ANALYZED
SAMPLE_SIZE
CHARACTER_SET_NAME The name of the character set: either CHAR_CS or NCHAR_CS
CHAR_COL_DECL_LENGTH
GLOBAL_STATS YES indicates that optimizer statistics are gathered or incrementally maintained. If this is not the case, the value is NO.
USER_STATS YES indicates that optimizer statistics were provided by a user. NO indicates they were gathered by Oracle.
AVG_COL_LEN The column's avarage amount of bytes used per record
CHAR_LENGTH For datatypes char, nchar, varchar2 and nvarchar2, the value of this colum corresponds to the (maximal) length of the values. See also CHAR_USED
CHAR_USED For datatypes char, nchar, varchar2 and nvarchar2, the value C indicates char length semantics, B byte length semantcis. See also CHAR_LENGTH
V80_FMT_IMAGE
DATA_UPGRADED
HIDDEN_COLUMN Indicator for hidden columns (YES or NO) only in dba_tab_cols
VIRTUAL_COLUMN Indicator for virtual columns (YES or NO) only in dba_tab_cols, see also the DATA_DEFAULT column and Identifying Virtual Columns in Oracle's Data Dictionary
SEGMENT_COLUMN_ID only in dba_tab_cols
INTERNAL_COLUMN_ID only in dba_tab_cols
HISTOGRAM If and what type of histogram statistics the optimizer stores for the column. Possible values are: NONE, FREQUENCY, TOP-FREQUENCY, HEIGHT BALANCED and HYBRID.
QUALIFIED_COL_NAME only in dba_tab_cols
DEFAULT_ON_NULL
IDENTITY_COLUMN YES indicates an identity column. See also the column DATA_DEFAULT.
SENSITIVE_COLUMN
EVALUATION_EDITION
UNUSABLE_BEFORE
UNUSABLE_BEGINNING
COLLATION
COLLATED_COLUMN_ID only in dba_tab_cols

Index