The ALL_TAB_COLUMNS view provides information on all columns in all user-defined tables and views.

ownerCHARACTER VARYINGUser name of the owner of the table or view in which the column resides.
schema_nameCHARACTER VARYINGName of the schema in which the table or view resides.
table_nameCHARACTER VARYINGName of the table or view.
column_nameCHARACTER VARYINGName of the column.
data_typeCHARACTER VARYINGData type of the column.
data_lengthNUMERICLength of text columns.
data_precisionNUMERICPrecision (number of digits) for NUMBER columns.
data_scaleNUMERICScale of NUMBER columns.
nullableCHARACTER(1)Whether or not the column is nullable. Possible values are: Y – column is nullable; N – column does not allow null.
column_idNUMERICRelative position of the column within the table or view.
data_defaultCHARACTER VARYINGDefault value assigned to the column.