easyMultiple Choice
FC0-U71 Practice Question: A user is unable to insert a new record into a…
A user is unable to insert a new record into a database table because a required field is missing. Which database concept enforces that a field must have a value?
⚠ Common exam trap
Test-takers frequently confuse the NOT NULL constraint with the primary key, thinking that a primary key's uniqueness property is what enforces a required value, but the primary key's NOT NULL behavior is a side effect, not its defining purpose.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
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NOT NULL constraint
A NOT NULL constraint is a database rule that prevents a field from containing a NULL value, ensuring that a value must be provided for that column when inserting or updating a record. In this scenario, the user cannot insert a new record because the required field is missing, which directly violates the NOT NULL constraint. This constraint is enforced at the database engine level, typically during the INSERT or UPDATE operation, and will raise an error if the field is omitted or set to NULL.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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NOT NULL constraint
Why this is correct
A NOT NULL constraint directly enforces that a column cannot store a missing value, rejecting any insert that omits the required field. This satisfies the stem's constraint precisely: the record fails because the mandatory field has no value, and NOT NULL is the mechanism that blocks such inserts at the database level.
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Primary key
Why it's wrong here
A primary key enforces uniqueness and non-null on its column, but the scenario concerns a non-key required field, which a NOT NULL constraint governs. It tempts because primary keys do reject nulls, yet they apply only to the designated key column, not to arbitrary required fields.
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Index
Why it's wrong here
An index speeds up data retrieval and can enforce uniqueness, but it does not require a column to hold a value. It tempts because unique indexes reject duplicates and nulls in some systems, yet the scenario needs a NOT NULL constraint on a non-key required field.
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Foreign key
Why it's wrong here
A foreign key enforces referential integrity between tables, requiring the value to match an existing parent key; it does not mandate that a column contain a value. It tempts because foreign keys do restrict inserts, but only when a referenced row is absent, not when a field is simply empty.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This FC0-U71 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the FC0-U71 exam.