How to print a field type on oracle without a `SELECT` - oracle

Question

Simple question:
How to print a field's type?
DESC TABLE_FOO.FIELD_FOO;
Results printing the whole table description.
How to print a specific field details with a command, i.e, without a SELECT?

Answer 1

There is no built-in way to do this, at least in any of the clients I've used. As mentioned in comments, describe is a client wrapper around a data dictionary query, and each client can implement it differently - SQL*Plus and SQL Developer seem to be slightly different, and no client is actually required to support this command at all.
Just for fun, if you really wanted to you could create a procedure to figure out and format the data type the same as desc, something like:
create or replace procedure col_data_type (p_table_name varchar2,
p_column_name varchar2)
as
l_data_type varchar2(30);
begin
select data_type
|| case when data_type = 'VARCHAR2' then '(' || data_length || ')' end
|| case when data_type = 'NUMBER' and data_precision is not null then
'(' || data_precision
|| case when data_scale is not null and data_scale > 0 then
',' || data_scale end
|| ')' end
into l_data_type
from user_tab_columns
where table_name = p_table_name
and column_name = p_column_name;
dbms_output.put_line(l_data_type);
end col_data_type;
/
Perhaps with more special formatting for other data types, but those are the obvious ones. You can then call that with execute. With a dummy table:
create table t42(i integer, n1 number, n2 number(10), n3 number(10,5),
v varchar2(10), c clob)
Then:
set serveroutput on
exec col_data_type('T42','I');
NUMBER
exec col_data_type('T42','N1');
NUMBER
exec col_data_type('T42','N2');
NUMBER(10)
exec col_data_type('T42','N3');
NUMBER(10,5)
exec col_data_type('T42','V');
VARCHAR2(10)
exec col_data_type('T42','C');
CLOB
Not entirely sure how useful that might be, or why you want to be able to do this at all. Also notice that it requires the client to be retrieving and displaying dbms_output buffer. You could make it a function instead, which puts you back to using a select, albeit a shorter one...

Answer 2

I don't believe it is possible to accomplish this without using a SELECT statement.
DESC OWNER.TABLE_NAME; is basically just running a query like this anyways (although not exactly the same, that depends on your client):
SELECT *
FROM ALL_TAB_COLS
WHERE OWNER = &theOwner
AND TABLE_NAME = &theTable;
If you want to only return a single column, you can do this:
SELECT *
FROM ALL_TAB_COLS
WHERE OWNER = &theOwner
AND TABLE_NAME = &theTable
AND COLUMN_NAME = &theColumn;
As #AlexPoole suggests, you could work around this by writing your own custom PROCEDURE or FUNCTION to return exactly what you need, but I believe the answer to the question "is there a built in command other than SELECT that does exactly what you need" is no, there is not.

Answer 3

I don't think you can do this without using a SELECT. You may be able to come up with some way to route the output of DESC to a file and then parse the file out to get what you want, but honestly - SELECT is going to be much easier.
Relational databases store the description of what they store in the database, where said description can be obtained in the same manner as any other information in the database, i.e. by using a SELECT to read it. The actual tables which store this are somewhat difficult to interpret, but happily Oracle has taken pity on us poor users and provided views which present this info in an easy-to-read manner. To get the type of a field you want to do a select one of the *_TAB_COLS views, where * is either USER, ALL, or DBA. The particular columns of interest are likely going to be COLUMN_NAME, DATA_TYPE, and DATA_LENGTH.
Share and enjoy.