What is the purpose of a NOT NULL constraint in SQL?

It ensures that a column can only contain unique values.

It ensures that a column cannot be null.

It ensures that a column can only contain numeric values.

It ensures that a column can only contain text values.

Which of the following is true about a primary key constraint in SQL?

It allows null values in the column.

It allows duplicate values in the column.

It uniquely identifies a row in a table.

It is not required for every table.

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?

ALTER TABLE Employees ADD CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);

ALTER TABLE Employees ADD PRIMARY KEY (EmployeeID);

ALTER TABLE Employees MODIFY PRIMARY KEY (EmployeeID);

ALTER TABLE Employees CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID);Output: No output.

Consider the following SQL table definition: CREATE TABLE Students ( StudentID INT PRIMARY KEY, StudentName VARCHAR(50), Age INT NOT NULL ); Which of the following SQL statements adds a foreign key constraint to the "DepartmentID" column referencing the "Department" table?

ALTER TABLE Students ADD CONSTRAINT FK_Students_Department FOREIGN KEY (DepartmentID) REFERENCES Department(DepartmentID);

ALTER TABLE Students ADD FOREIGN KEY (DepartmentID) REFERENCES Department(DepartmentID);

ALTER TABLE Students MODIFY FOREIGN KEY (DepartmentID) REFERENCES Department(DepartmentID);

ALTER TABLE Students CONSTRAINT FK_Students_Department FOREIGN KEY (DepartmentID) REFERENCES Department(DepartmentID);Output: No output.

Consider the following SQL table definition: CREATE TABLE Orders ( OrderID INT PRIMARY KEY, OrderDate DATE, TotalAmount DECIMAL(10, 2) ); Which of the following SQL statements adds a check constraint to the "TotalAmount" column to ensure that the value is greater than zero?

ALTER TABLE Orders ADD CONSTRAINT CHK_Orders_TotalAmount CHECK (TotalAmount > 0);

ALTER TABLE Orders ADD CHECK CONSTRAINT (TotalAmount > 0);

ALTER TABLE Orders MODIFY CONSTRAINT CHK_Orders_TotalAmount CHECK (TotalAmount > 0);

ALTER TABLE Orders CONSTRAINT CHK_Orders_TotalAmount CHECK (TotalAmount > 0);Output: No output.

Consider the following SQL table definition: CREATE TABLE Products ( ProductID INT PRIMARY KEY, ProductName VARCHAR(50) UNIQUE, Price DECIMAL(10, 2) NOT NULL ); Which of the following SQL statements alters the "Price" column to allow NULL values?

ALTER TABLE Products MODIFY COLUMN Price NULL;

ALTER TABLE Products ALTER COLUMN Price NULL;

ALTER TABLE Products ALTER Price NULL;

ALTER TABLE Products SET NULL Price;Output: No output.

Consider the following SQL table definition: CREATE TABLE Customers ( CustomerID INT PRIMARY KEY, CustomerName VARCHAR(50) NOT NULL, Email VARCHAR(50) UNIQUE ); Which of the following SQL statements drops the unique constraint on the "Email" column?

ALTER TABLE Customers DROP CONSTRAINT UNIQUE Email;

ALTER TABLE Customers DROP UNIQUE Email;

ALTER TABLE Customers DROP CONSTRAINT UQ_Customers_Email;

ALTER TABLE Customers DROP UQ_Customers_Email;Output: No output.

Consider the following SQL table definition: CREATE TABLE Books ( BookID INT PRIMARY KEY, BookName VARCHAR(50), AuthorID INT, FOREIGN KEY (AuthorID) REFERENCES Authors(AuthorID) ON DELETE CASCADE ); Which of the following constraints is specified in the table definition?

Foreign Key ConstraintOutput: No output.

Consider the following SQL table definition: CREATE TABLE Products ( ProductID INT PRIMARY KEY, ProductName VARCHAR(50), CategoryID INT, CONSTRAINT CHK_Products_Category CHECK (CategoryID IN (1, 2, 3)) ); Which of the following constraints restricts the possible values of the "CategoryID" column to a specific set of values?

Check ConstraintOutput: No output.

Consider the following SQL table definition: CREATE TABLE Employees ( EmployeeID INT PRIMARY KEY, EmployeeName VARCHAR(50), DepartmentID INT ); Which of the following SQL statements adds a foreign key constraint to the "DepartmentID" column referencing the "Departments" table, where the "DepartmentID" column in the "Departments" table is defined as UNIQUE?

ALTER TABLE Employees ADD CONSTRAINT FK_Employees_Departments FOREIGN KEY (DepartmentID) REFERENCES Departments(DepartmentID);

ALTER TABLE Employees ADD FOREIGN KEY (DepartmentID) REFERENCES Departments(DepartmentID);

ALTER TABLE Employees MODIFY FOREIGN KEY (DepartmentID) REFERENCES Departments(DepartmentID);

ALTER TABLE Employees CONSTRAINT FK_Employees_Departments FOREIGN KEY (DepartmentID) REFERENCES Departments(DepartmentID);Output: No output.

Consider the following SQL table definition: CREATE TABLE Students ( StudentID INT PRIMARY KEY, StudentName VARCHAR(50), Age INT ); Which of the following SQL statements adds a unique constraint to the "StudentName" column?

ALTER TABLE Students ADD CONSTRAINT UQ_Students_StudentName UNIQUE (StudentName);

ALTER TABLE Students ADD UNIQUE (StudentName);

ALTER TABLE Students MODIFY UNIQUE (StudentName);

e);b) ALTER TABLE Students ADD UNIQUE (StudentName);c) ALTER TABLE Students MODIFY UNIQUE (StudentName);

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