Multiple choice

Which of the following the correct way of defining the PRIMARY KEY constraint for a STUDENT table A. CREATE TABLE STUDENTS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , MARKS INT,
PRIMARY KEY (ID) );

B. CREATE TABLE STUDENTS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , MARKS INT,
PRIMARY KEY (ID, NAME) );

C. CREATE TABLE STUDENTS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , MARKS INT,
); ALTER TABLE STUDENTS ADD CONSTRAINT PK_STUDENTID PRIMARY KEY (ID, NAME);

D. CREATE TABLE STUDENTS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , MARKS INT,
); ALTER TABLE STUDENTS ADD CONSTRAINT PK_STUDENTID PRIMARY KEY (ID);

  1. A and C are correct

  2. B and D are correct

  3. A, B and C are correct

  4. A, B and D are correct

  5. All 4 are correct
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

A. Correct, defining the PRIMARY KEY along with the table creation for a single column. B. Correct, defining the PRIMARY KEY along with the table creation for multiple columns, this is called composite primary key. C. Correct, defining a PRIMARY KEY using ALTER statement for multiple column after the creation of the table. This is called composite primary key. D. Correct,  defining a PRIMARY KEY using ALTER statement for one column after the creation of the table.  

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