TheABS()function in SQL returns theabsolute valueof a given number, effectively measuring itsdistance from zero.
Example Usage:
sql
SELECT ABS(-50), ABS(50);
Result:
50 | 50
* This function ensures that numbers arealways positive, regardless of their original sign.
Why Other Options Are Incorrect:
* Option A (CONCAT) (Incorrect):Used tocombine strings(not numbers).
* Option B (LOWER) (Incorrect):Converts text tolowercase, not numerical operations.
* Option C (FROM) (Incorrect):Part of SELECT FROM queries,not a function.
Thus, the correct choice isABS(), which computes the absolute value of a number.

Cardinalitydefines theminimum and maximum number of occurrencesof one entity in relation to another.
Example Usage in an ER Model:
* One-to-Many (1:M): Acustomer can place multiple orders, but each order belongs to onlyone customer.
Customers (1) --- (M) Orders
* Cardinality notation:
(1,1) # One-to-One
(0,M) # Zero-to-Many
(1,M) # One-to-Many
Why Other Options Are Incorrect:
* Option B (Physical design) (Incorrect):Focuses onstorage and indexing, not relationships.
* Option C (Attribute minimum) (Incorrect):No such formal term in database modeling.
* Option D (Partition) (Incorrect):Refers todividing tables, not relationship constraints.
Thus, the correct answer isCardinality, as it definesmin/max constraints on relationships.

Thecorrect syntaxfor inserting a new row into a table follows this structure:
Standard SQL INSERT Syntax:
sql
INSERT INTO TableName (Column1, Column2, ...)
VALUES (Value1, Value2, ...);
For this scenario:
sql
INSERT INTO Employee (Name) VALUES ('John Doe');
Why Other Options Are Incorrect:
* Option A (Incorrect):Uses incorrect syntax { ... }, which isnot valid SQL syntax.
* Option C (Incorrect):Does not specify the column name, whichcauses an error.
* Option D (Incorrect):Misses theINTOkeyword, which is required in standard SQL.
Thus, the correct syntax isOption B, ensuring aproperly formatted insert statement.

Toadd a primary key constraint after table creation, we use theALTER TABLEstatement.
Example Usage:
sql
ALTER TABLE Employees
ADD CONSTRAINT PK_Employees PRIMARY KEY (EmpID);
* Thisaddsa primary key to the EmpID columnafter the table was created.
Why Other Options Are Incorrect:
* Option B (CREATE TABLE) (Incorrect):Used for defining constraintsduringtable creation, not after.
* Option C (UPDATE) (Incorrect):Modifiesrow values, not constraints.
* Option D (INSERT INTO) (Incorrect):Used toadd datato a table, not modify constraints.
Thus, the correct answer isALTER TABLE, as itmodifies table structure to add a primary key constraint.

Indatabase modeling, the relationship between asupertype and its subtypesis called anIsA relationship.
Example Usage:
* AVehicle supertypemay haveCar and Truck subtypes.
Vehicle
### Car
### Truck
* InER diagrams, this is represented as:
Vehicle (Supertype)
|
### Car (Subtype)
### Truck (Subtype)
* SQL Table Implementation:
sql
CREATE TABLE Vehicle (
VehicleID INT PRIMARY KEY,
Make VARCHAR(50),
Model VARCHAR(50)
);
CREATE TABLE Car (
VehicleID INT PRIMARY KEY,
FOREIGN KEY (VehicleID) REFERENCES Vehicle(VehicleID),
EngineType VARCHAR(50)
);
CREATE TABLE Truck (
VehicleID INT PRIMARY KEY,
FOREIGN KEY (VehicleID) REFERENCES Vehicle(VehicleID),
CargoCapacity INT
);
* This structurepreserves the IsA relationshipbetween Vehicle (supertype) and Car/Truck (subtypes).
Why Other Options Are Incorrect:
* Option A (Strong entity) (Incorrect):Strong entitiesdo not rely on a supertype/subtype hierarchy.
* Option C (Associative entity) (Incorrect):Used toresolve many-to-many relationships, not supertype
/subtype relationships.
* Option D (Weak entity) (Incorrect):Weak entitiesdepend on a strong entity, but supertype-subtype relations useinheritance(not dependency).
Thus, the correct answer isIsA relationship, as it describes theinheritance hierarchybetweensupertypes and subtypes.