SQL Data Definition Language (DDL) 2

Question 1

Which DDL command removes an entire table including its structure and all data?

Accepted Answer

DROP TABLE

Answer

DELETE TABLE

Answer

TRUNCATE TABLE

Answer

REMOVE TABLE

Question 2

What is the key difference between TRUNCATE and DELETE?

Accepted Answer

TRUNCATE cannot be filtered with WHERE and resets storage

Answer

TRUNCATE removes the table structure

Answer

DELETE is faster than TRUNCATE

Answer

TRUNCATE only works on views

Question 3

Which command adds a new column to an existing table?

Accepted Answer

ALTER TABLE ... ADD COLUMN

Answer

MODIFY TABLE ... NEW COLUMN

Answer

UPDATE TABLE ... ADD

Answer

INSERT COLUMN INTO

Question 4

Why is TRUNCATE classified as DDL rather than DML?

Accepted Answer

It operates at the table-structure level and is not transaction-logged per row

Answer

It returns a result set

Answer

It requires a WHERE clause

Answer

It only affects indexes

Question 5

Which statement renames an existing database object in standard SQL?

Accepted Answer

RENAME TABLE / ALTER TABLE ... RENAME

Answer

CHANGE TABLE NAME

Answer

UPDATE TABLE NAME

Answer

SET TABLE NAME

Question 6

What does the CREATE INDEX statement accomplish?

Accepted Answer

Creates a structure to speed up data retrieval on specified columns

Answer

Inserts rows faster by caching them

Answer

Deletes duplicate rows

Answer

Encrypts a column

Question 7

After issuing a DROP COLUMN with ALTER TABLE, what happens to that column's data?

Accepted Answer

It is permanently removed

Answer

It is moved to a backup table

Answer

It is hidden but recoverable with ROLLBACK

Answer

It becomes NULL but stays