Column Information

While the USER_TABLES view provides information on your table names and storage, USER_TAB_COLUMNS is used to obtain detailed information of each column of a table.
- Column names,
- Column data types
- Length of data types
- Precision and scale for NUMBER columns
- Whether null are allowed
- Default value.

DESCRIBE user_tab_columns;

Name	Null?	Type
TABLE_NAME	NOT NULL	VARCHAR2(30)
COLUMN_NAME	NOT NULL	VARCHAR2(30)
DATA_TYPE		VARCHAR2(106)
DATA_TYPE_MOD		VARCHAR2(3)
DATA_TYPE_OWNER		VARCHAR2(30)
DATA_LENGTH	NOT NULL	NUMBER
DATA_PRECISION		NUMBER
DATA_SCALE		NUMBER
NULLABLE		VARCHAR2(1)
COLUMN_ID		NUMBER

................more..

SELECT column_name, data_type, data_length, data_precision, data_scale, nullable
FROM user_tab_columns WHERE table_name = 'EMPLOYEES';

COLUMN_NAME	DATA_TYPE	DATA_LENGTH	DATA_PRECISION	DATA_SCALE	NUL
EMPLOYEE_ID	NUMBER	22	6	0	N
FIRST_NAME	VARCHAR2	20			Y
LAST_NAME	VARCHAR2	25			N
EMAIL	VARCHAR2	25			N
PHONE_NUMBER	VARCHAR2	20			Y
HIRE_DATE	DATE	7			N
JOB_ID	VARCHAR2	10			N
SALARY	NUMBER	22	8	2	Y
COMMISSION_PCT	NUMBER	22	2	2	Y
MANAGER_ID	NUMBER	22	6	0	Y
DEPARTMENT_ID	NUMBER	22	4	0	Y

11 rows selected.