Data Definition Language (DDL) Flashcards
7 cards from real SQL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Data Definition Language (DDL) flashcards as text
Are DDL statements in most databases implicitly committed?
Answer: Yes, most DDL auto-commits the current transaction
In most RDBMSs, DDL statements cause an implicit commit, making the change permanent immediately.
Which object does CREATE SEQUENCE generate?
Answer: An object that produces a series of unique numeric values
CREATE SEQUENCE defines a number generator commonly used to supply unique key values.
What is the purpose of a temporary table created with CREATE TEMPORARY TABLE?
Answer: It exists only for the session or transaction and is dropped automatically
A temporary table lives only for the duration of the session or transaction and is then automatically removed.
Which statement best describes the relationship between DDL and the data dictionary?
Answer: DDL modifies the metadata describing database objects
DDL commands update the data dictionary (system catalog) that stores definitions of database objects.
What does ALTER TABLE ... DROP CONSTRAINT do?
Answer: Removes a named constraint from the table
DROP CONSTRAINT removes a specified constraint definition while leaving the table and its data intact.
Which DDL command would you use to create a database object that enforces a value list like ('S','M','L')?
Answer: A CHECK constraint or an ENUM/domain type
A CHECK constraint (or an ENUM/domain in some systems) restricts a column to a defined set of allowed values.
What distinguishes COMMENT ON (or column comments) as a DDL feature?
Answer: It attaches descriptive metadata to database objects
COMMENT ON adds human-readable documentation as metadata to tables, columns, or other objects.