Which statement about primary keys in a relational database table is completely true? MCQ with Answer and Explanation

Question
Which statement about primary keys in a relational database table is completely true?
A. A table can contain at most one primary key.
B. Primary keys must always be numeric integers.
C. A primary key column can accept a single NULL value.
D. A table can have multiple distinct primary keys.
Answer: Option A
Solution (By JKSSB Mock Tests)
A relational database table can have exactly one primary key constraint defined, which uniquely identifies each record and strictly forbids NULLs.
This question belongs to: Computer Database Management System (DBMS)
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Practice More Database Management System (DBMS) Questions

Question #1
Which SQL function returns the average of a numeric column?
A. AVG()
B. COUNT()
C. SUM()
D. MEAN()
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Correct Answer: Option A

Explanation:
AVG() calculates the average of the values in a numeric column.
This question belongs to: Computer Database Management System (DBMS)
Question #2
Which of the following is a valid SQL string function?
A. CONCAT
B. SUBSTRING
C. All of the above
D. REPLACE
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Correct Answer: Option C

Explanation:
SUBSTRING, CONCAT, and REPLACE are common string functions in SQL.
This question belongs to: Computer Database Management System (DBMS)
Question #3
Which of the following is a valid SQL command to delete a database?
A. DELETE DATABASE
B. TRUNCATE DATABASE
C. DROP DATABASE
D. REMOVE DATABASE
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Correct Answer: Option C

Explanation:
DROP DATABASE is the SQL command to delete an entire database.
This question belongs to: Computer Database Management System (DBMS)
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