Column definition for a specific column in a view

Question

Is there a way to query the metadata to get the definition of a single column in a view? I can see the complete DDL for a view from USER_VIEWS.TEXT, and I can see the column listing in USER_TAB_COLUMNS to give the datatype etc. However, what I'm looking for is the DDL that defined a specific column.
So, given:
create table PERSON (
SSN VARCHAR2(12),
FIRST_NAME VARCHAR2(25),
LAST_NAME VARCHAR2(25),
STREET VARCHAR2(40),
CITY VARCHAR2(30),
STATE VARCHAR2(30),
ZIP VARCHAR2(15),
COUNTRY VARCHAR2(35))
create view PERSON_VW as
select SSN,
FIRST_NAME,
LAST_NAME,
FIRST_NAME || ' ' || LAST_NAME FULL_NAME
from PERSON
I expect the query might look something like:
select DDL from metadata where table_name = 'PERSON_VW' and column_name = 'FULL_NAME'
and the result would be: "PERSON.FIRST_NAME || ' ' || PERSON.LAST_NAME"
or select DDL from metadata where table_name = 'PERSON_VW' and column_name = 'FIRST_NAME'
and the result would be: "PERSON.FIRST_NAME"
Thanks!

Answer 1

>
Hi again Barry,
When I queried user_tab_columns (or dba_tab_columns or all_tab_columns), I have the following list of columns:
TABLE_NAME
COLUMN_NAME
DATA_TYPE
DATA_LENGTH
DATA_PRECISION
DATA_SCALE
NULLABLE
COLUMN_ID
DEFAULT_LENGTH
DATA_DEFAULT
I don't see anything resembling the DDL for the view column. Somewhere underneath some
cover I haven't peeked under, Oracle must be keeping track of what it is supposed to be giving
for, in my example, FULL_NAME.Unless I'm very much mistaken, these columns' data (per table) looks pretty much like DDL to me.
Maybe what you need is just SQL Developer (great tool, if you don't have it, get it!).
And it's free (as in beer - not as in speech! :( )
Beside the connections tab is a "Reports" tab with various, as you might expect ;), reports.
One of them is on the Tables - with (some) DDL. This will work as a once-off if that's what
you need?
Otherwise there's the SQL tab if you open a table under connections - it's very complete - sample
at bottom of post.
HTH,
Paul...
(Ultimately, I'm diagnosing problems in existing databases that have views already created so
I don't have the option of considering virtual columns.)Quelle surprise ;(
Paul...
-Barry
CREATE TABLE "HR"."COUNTRIES"
    "COUNTRY_ID"   CHAR(2 BYTE) CONSTRAINT "COUNTRY_ID_NN" NOT NULL ENABLE,
    "COUNTRY_NAME" VARCHAR2(40 BYTE),
    "REGION_ID"    NUMBER,
    CONSTRAINT "COUNTRY_C_ID_PK" PRIMARY KEY ("COUNTRY_ID") ENABLE,
    CONSTRAINT "COUNTR_REG_FK" FOREIGN KEY ("REGION_ID") REFERENCES "HR"."REGIONS" ("REGION_ID") ENABLE
  ORGANIZATION INDEX NOCOMPRESS PCTFREE 10 INITRANS 2 MAXTRANS 255 LOGGING STORAGE
    INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT
  TABLESPACE "USERS" PCTTHRESHOLD 50;
COMMENT ON COLUMN "HR"."COUNTRIES"."COUNTRY_ID"
IS
  'Primary key of countries table.';
  COMMENT ON COLUMN "HR"."COUNTRIES"."COUNTRY_NAME"
IS
  'Country name';
  COMMENT ON COLUMN "HR"."COUNTRIES"."REGION_ID"
IS
  'Region ID for the country. Foreign key to region_id column in the departments table.';
  COMMENT ON TABLE "HR"."COUNTRIES"
IS
  'country table. Contains 25 rows. References with locations table.';