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Oracle Database Interview Question:
How To View All Columns in an Existing Table?
Submitted by: AdministratorIf you have an existing table and want to know how many columns are in the table and how they are defined, you can use the system view USER_TAB_COLUMNS as shown in the following tutorial exercise:
SQL> COL data_type FORMAT A12;
SQL> SELECT column_name, data_type, data_length
FROM user_tab_columns WHERE table_name = 'EMPLOYEES';
<pre>COLUMN_NAME DATA_TYPE DATA_LENGTH
------------------------------ ------------ -----------
EMPLOYEE_ID NUMBER 22
FIRST_NAME VARCHAR2 20
LAST_NAME VARCHAR2 25
EMAIL VARCHAR2 25
PHONE_NUMBER VARCHAR2 20
HIRE_DATE DATE 7
JOB_ID VARCHAR2 10
SALARY NUMBER 22
COMMISSION_PCT NUMBER 22
MANAGER_ID NUMBER 22
DEPARTMENT_ID NUMBER 22</pre>
Submitted by: Administrator
SQL> COL data_type FORMAT A12;
SQL> SELECT column_name, data_type, data_length
FROM user_tab_columns WHERE table_name = 'EMPLOYEES';
<pre>COLUMN_NAME DATA_TYPE DATA_LENGTH
------------------------------ ------------ -----------
EMPLOYEE_ID NUMBER 22
FIRST_NAME VARCHAR2 20
LAST_NAME VARCHAR2 25
EMAIL VARCHAR2 25
PHONE_NUMBER VARCHAR2 20
HIRE_DATE DATE 7
JOB_ID VARCHAR2 10
SALARY NUMBER 22
COMMISSION_PCT NUMBER 22
MANAGER_ID NUMBER 22
DEPARTMENT_ID NUMBER 22</pre>
Submitted by: Administrator
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