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

DROP TABLE deletes the table definition along with all its data and indexes.

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 all rows without a WHERE clause and generally resets the table more efficiently than DELETE.

Question 3

Which command adds a new column to an existing table?

Accepted Answer

ALTER TABLE ... ADD COLUMN

Answer

ALTER TABLE with ADD COLUMN modifies an existing table's structure by adding a column.

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

TRUNCATE deallocates data pages at the structural level rather than logging individual row deletions, so it is treated as DDL.

Question 5

Which statement renames an existing database object in standard SQL?

Accepted Answer

RENAME TABLE / ALTER TABLE ... RENAME

Answer

Renaming is done via ALTER TABLE ... RENAME (or RENAME TABLE in some dialects), both DDL operations.

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