Final answer:
The statement that is not true for an ideal primary key is that it should be a composite of several long attributes. Ideal primary keys should be fixed, short, and can be numeric or alphanumeric for efficiency and simplicity.
Step-by-step explanation:
The question pertains to the characteristics of an ideal primary key in the context of database design and management. An ideal primary key should have the following traits: it should be fixed, meaning it doesn't change over time; it should preferably be short to ensure efficiency in database operations; and while it can be numeric or alphanumeric, simplicity is generally preferred. Therefore, the statement that is not true for an ideal primary key is c) A composite of several long attributes. Composite keys that are long can be unwieldy and negatively impact the performance of a database. A primary key's main function is to uniquely identify each record in a table, and this can be efficiently achieved with a shorter and simpler key.