SQL Tutorial : DDL - DROP, TRUNCATE

SQL Tutorial : DDL - DROP, TRUNCATE

Let's learn about next topic: DROP & TRUNCATE

- DROP TABLE STUDENTS => REMOVES THE TABLE PERMANENTLY

- TRUNCATE :

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1.DELETE THE DATA PERMANENTLY

2.NO ROLLBACK

3.RELEASES THE MEMORY PACES OCCUPIED BY DATA

4.NO CONDITIONAL DELETION

5.DOES NOT INITIATE A TRIGGER

6.TRUNCATE IS FASTER

- ALTER TABLE DEPS

SET UNUSED COLUMN DNAME2

- ALTER TABLE DEPS

DROP UNUSED COLUMNS

DD: USER_TABLES

- CREATE TABLE COPY_EMP

AS

SELECT EMPLOYEE_ID,LAST_NAME,SALARY

FROM EMPLOYEES

WHERE DEPARTMENT_ID=60

- CREATE TABLE COPY_EMP

AS

SELECT EMPLOYEE_ID,LAST_NAME,SALARY

FROM EMPLOYEES

WHERE DEPARTMENT_ID=6

- ONLY NOT NULL CONSTRAINTS ARE COPIED