identify difference from NUMBER(5) and NUMBER(8,2) USER_TAB_COLUMNS

Question

I want to get the columns names and datatype and its datatype\'s length .as example

if there is a table

SQL> create table TestTable(
  2    ID                


        

Answer 1

There are data_precision and data_scale columns there.
Please take a look at this example:

create table qwer(
  x number,
  y number(8,2),
  z number(5,0),
  a int,
  b decimal(5,3)
);

SELECT column_name, data_type, data_precision, data_scale
FROM USER_TAB_COLUMNS
WHERE Table_name = 'QWER'
;

COLUMN_NAME   DATA_TYPE DATA_PRECISION DATA_SCALE
------------- --------- -------------- ----------
B             NUMBER     5             3
A             NUMBER
X             NUMBER         
Y             NUMBER     8             2
Z             NUMBER     5             0

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EDIT

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To find primary key columns you need to join two dictionary views, please see the below example:

CREATE TABLE pk1(
  id int primary key,
  name varchar2(10)
);

CREATE TABLE pk2(
  id int ,
  pk1 number(10,0),
  pk2 varchar2(5),
  name varchar2(10),
  constraint my_composite_pk primary key (id, pk1, pk2 )
);

SELECT c.table_name, cols.column_name, cols.position 
FROM user_constraints c
JOIN USER_CONS_COLUMNS cols
USING ( CONSTRAINT_NAME )
WHERE c.table_name IN ('PK1', 'PK2' )
  and c.constraint_type = 'P' /* P - means PRIMARY KEY */
ORDER BY 1,3
; 

TABLE_NAME COLUMN_NAME   POSITION
---------- ----------- ----------
PK1        ID                   1
PK2        ID                   1
PK2        PK1                  2
PK2        PK2                  3