Data manipulation language (DML) commands are used to define a database, including creating, altering, and dropping tables and establishing constraints.

The keyword LIKE can be used in a WHERE clause to refer to a range of values.

Assertion. There is a difference between a field being empty or storing NULL value in a field.

Reason. The NULL value is a legal way of signifying that no value exists in the field.

Assertion. The ALL and DISTINCT clauses of a SELECT query are related.

Reason. The ALL clause is the opposite of the DISTINCT clause of a SELECT Query.