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Consider the following SQL table definition:
CREATE TABLE Employees (
EmployeeID INT,
EmployeeName VARCHAR(50),
DepartmentID INT
);
EmployeeID INT,
EmployeeName VARCHAR(50),
DepartmentID INT
);
Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?
- a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);
- b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);
- c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);
- d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
Consider the following SQL table definition:CREATE TABLE Employees (Em...
The ALTER TABLE statement is used to modify an existing table. To add a primary key constraint to the "EmployeeID" column, the correct syntax is to use the CONSTRAINT keyword followed by the constraint name (e.g., PK_Employees) and the PRIMARY KEY keyword.
Most Upvoted Answer
Consider the following SQL table definition:CREATE TABLE Employees (Em...
Understanding Primary Key Constraints
In SQL, a primary key constraint ensures that a column (or a set of columns) contains unique values and cannot be NULL. In the case of the `Employees` table, the `EmployeeID` column is intended to serve as the unique identifier for each employee.
Evaluating the Options
Let's break down each of the provided SQL statements to understand why option 'A' is correct:
Option A: Correct Syntax
- `ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);`
- This statement correctly adds a primary key constraint named `PK_Employees` to the `EmployeeID` column.
- It follows the correct SQL syntax for adding constraints.
Option B: Missing Constraint Name
- `ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);`
- While this statement would technically work to add a primary key, it lacks a specific name for the constraint.
- Naming constraints is a best practice for easier reference.
Option C: Incorrect Modification
- `ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);`
- This statement is incorrect because the `MODIFY` keyword is not valid for adding a primary key constraint.
- It suggests altering an existing constraint, which is not applicable here.
Option D: Syntax Error
- `ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);`
- This option misses the `ADD` keyword, which is necessary to introduce a new constraint.
- Thus, it results in a syntax error.
Conclusion
The correct choice is option 'A' as it adheres to the standard SQL syntax for adding a primary key constraint, ensuring the `EmployeeID` column is uniquely identified and cannot have NULL values.
In SQL, a primary key constraint ensures that a column (or a set of columns) contains unique values and cannot be NULL. In the case of the `Employees` table, the `EmployeeID` column is intended to serve as the unique identifier for each employee.
Evaluating the Options
Let's break down each of the provided SQL statements to understand why option 'A' is correct:
Option A: Correct Syntax
- `ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);`
- This statement correctly adds a primary key constraint named `PK_Employees` to the `EmployeeID` column.
- It follows the correct SQL syntax for adding constraints.
Option B: Missing Constraint Name
- `ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);`
- While this statement would technically work to add a primary key, it lacks a specific name for the constraint.
- Naming constraints is a best practice for easier reference.
Option C: Incorrect Modification
- `ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);`
- This statement is incorrect because the `MODIFY` keyword is not valid for adding a primary key constraint.
- It suggests altering an existing constraint, which is not applicable here.
Option D: Syntax Error
- `ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);`
- This option misses the `ADD` keyword, which is necessary to introduce a new constraint.
- Thus, it results in a syntax error.
Conclusion
The correct choice is option 'A' as it adheres to the standard SQL syntax for adding a primary key constraint, ensuring the `EmployeeID` column is uniquely identified and cannot have NULL values.
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Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer?
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Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer?.
Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer?.
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Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer?, a detailed solution for Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? has been provided alongside types of Consider the following SQL table definition:CREATE TABLE Employees (EmployeeID INT,EmployeeName VARCHAR(50),DepartmentID INT);Which of the following SQL statements adds a primary key constraint to the "EmployeeID" column?a)ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);b)ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);c)ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);d)ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.Correct answer is option 'A'. Can you explain this answer? theory, EduRev gives you an
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