SQL · Question 4 · Easy
Which constraint ensures that all non-NULL values in a column are distinct and, unlike PRIMARY KEY, allows the column to contain NULL?
- PRIMARY KEY
- UNIQUE
- CHECK
- FOREIGN KEY
Answer and explanation
Answer: B. UNIQUE
Explanation: UNIQUE enforces distinct values but allows NULLs. PRIMARY KEY is both unique and NOT NULL.
Previous: Which SQL command removes all rows from a table but keeps the table structure… · Next: Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
Practise sql
Try a fresh set of sql questions with an explanation after every answer, free and without signing up: SQL practice. Or sit a full placement mock test.
More sql questions
- Which SQL clause is used to filter groups formed by GROUP BY, for example to…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Which SQL command removes all rows from a table but keeps the table structure…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Using a table Employee(id, name, dept, salary), which of the following queries…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
- Table Employee: id | name | dept | salary 1 | Asha | HR | 30000 2 | Ravi | IT…
More technical & programming practice
Operating Systems · Computer Networks · Software Engineering · Cloud & DevOps · GenAI Basics · Pseudo-code · C Programming · Java
LogicWiz Exams home · All practice topics · Placement mock tests · Daily 10 challenge