In a database, what does a NULL value in the Phone column mean?
Dans une base de données, que signifie une valeur NULL dans la colonne Téléphone ?
Answers
AThe phone number is 0, stored as a number in the columnLe numéro de téléphone vaut 0, stocké comme un nombre dans la colonne
BThe phone number is an empty string of spacesLe numéro est une chaîne vide composée d'espaces
CThe row has been deletedLa ligne a été supprimée
DThe value is missing or unknownLa valeur est manquante ou inconnue
The answer and explanation are in the full bank.
This question is one of 2,831 in the paid banks. Each comes with the correct answer and the reasoning behind it, not just a mark.
Unlock for 5,000 RWFMIFOTRA exam practicealigned to Practice set: Database Management·2 marks·Medium
More Database questions
- What is the main role of a database management system (DBMS) such as PostgreSQL, MySQL or SQL Server?
- In a relational table called Applicants, what does a single row represent?
- Which two properties must every primary key value have?
- The Employees table has a DistrictID column that must always refer to an existing row in the Districts table. What enforces this rule?
- An ExamResults table records one score per candidate per paper. Neither CandidateID nor PaperID is unique on its own. What is a suitable primary key?
- A designer gives each applicant an auto-generated ApplicantID as the primary key, and stores the national ID number as a separate unique column. Why use this surrogate key?
- One district has many sectors, and each sector belongs to exactly one district. What type of relationship is this?
- Each trainee can attend many courses, and each course has many trainees. How is this relationship stored in a relational database?