Programming Concepts: Python and MySQL Practice MCQs

Question 1

A company uses MySQL to store employee records in company_db. Which description correctly separates these terms?

Accepted Answer

A. MySQL is the DBMS, company_db is a database, and SQL is the language used to work with it.

Answer

MySQL is the DBMS, company_db is a database, and SQL is the language used to work with it.

Answer

SQL is the database and company_db is its storage engine.

Answer

MySQL is a table inside the SQL database.

Answer

company_db is the programming language used by MySQL.

Question 2

A newly created table has six columns and no rows. What are its degree and cardinality?

Accepted Answer

B. Degree 6 and cardinality 0.

Answer

Degree 0 and cardinality 6.

Answer

Degree 6 and cardinality 0.

Answer

Both are 6 because the table exists.

Answer

Both are 0 until the first insert.

Question 3

Which statement about CREATE SCHEMA and CREATE DATABASE is correct in MySQL?

Accepted Answer

C. They are synonyms for creating a database.

Answer

CREATE SCHEMA creates only a single table.

Answer

A schema must be created inside every MySQL database.

Answer

They are synonyms for creating a database.

Answer

CREATE DATABASE creates rows but CREATE SCHEMA creates columns.

Question 4

Each department has many employees, while each employee belongs to at most one department. Where should the department reference normally be stored?

Accepted Answer

D. In the employee table as a foreign key.

Answer

In separate employee1, employee2 and employee3 columns in department.

Answer

Only in a text description of the relationship.

Answer

In department as one unique employee name.

Answer

In the employee table as a foreign key.

Question 5

An employee may have several independently managed phone numbers. Which design best represents this?

Accepted Answer

A related phone table with one row per employee–phone association.

Answer

One INT column storing all numbers joined together.

Answer

A fixed set of two phone columns regardless of requirements.

Answer

A primary key on the employee's name for every phone number.

Question 6

An order line is identified by an order ID together with a line number that repeats across orders. Which explanation fits?

Accepted Answer

B. The line depends on its owner for identification and can use a composite key.

Answer

The line number alone must be globally unique.

Answer

The line depends on its owner for identification and can use a composite key.

Answer

The order cannot have more than one line.

Answer

A foreign key automatically makes the line number unique.

Question 7

Which declaration can identify an employee–project assignment without preventing either side from appearing in other assignments?

Accepted Answer

C. PRIMARY KEY (employee_id, project_id)

Answer

UNIQUE (employee_id), UNIQUE (project_id)

Answer

PRIMARY KEY (employee_id)

Answer

PRIMARY KEY (employee_id, project_id)

Answer

PRIMARY KEY (project_id)

Question 8

Which requirement distinguishes a candidate key from an arbitrary superkey?

Accepted Answer

D. It is minimal: no attribute can be removed while preserving identification.

Answer

It must always contain exactly one column.

Answer

It must be the key chosen as PRIMARY KEY.

Answer

It must refer to another table.

Answer

It is minimal: no attribute can be removed while preserving identification.

Question 9

A table declares PRIMARY KEY (employee_id, project_id). Which pair can be added when (101, 7) already exists, assuming both referenced parents exist?

Accepted Answer

A. (101, 8)

Answer

(101, 8)

Answer

(101, 7)

Answer

(NULL, 8)

Answer

(102, NULL)

Question 10

Which statement about primary keys is correct?

Accepted Answer

B. A table can have one primary-key constraint containing several columns.

Answer

A table can have a separate primary key for every candidate key.

Answer

A table can have one primary-key constraint containing several columns.

Answer

A composite primary key allows NULL in all but its first column.

Answer

MySQL cannot create any table without a declared primary key.

Question 11

An employee table allows department_id to be NULL and references department. Which insertion is valid, assuming all other column rules are satisfied?

Accepted Answer

C. A row with department_id NULL.

Answer

A row with department_id 99 when department 99 is absent.

Answer

A row whose department_id uses a department name instead of the defined integer key.

Answer

A row with department_id NULL.

Answer

A row with any non-NULL department_id because foreign keys only document relationships.

Question 12

Two employees belong to department 10. Must their department_id values differ?

Accepted Answer

D. No; foreign-key values can repeat in a one-to-many relationship.

Answer

Yes; every foreign key is automatically UNIQUE.

Answer

Yes; the parent primary key makes all child columns primary keys.

Answer

No, but only if referential integrity is disabled.

Answer

No; foreign-key values can repeat in a one-to-many relationship.

Question 13

Which type is most appropriate for an exact amount requiring two decimal places?

Accepted Answer

A. DECIMAL(10,2)

Answer

DECIMAL(10,2)

Answer

FLOAT solely because all decimal values are exact in floating point.

Answer

INT without any scaling convention.

Answer

DATE

Question 14

How many digits before the decimal point can DECIMAL(10,2) represent?

Accepted Answer

B. 8

Answer

10

Answer

8

Answer

12

Answer

2

Question 15

Why is a phone number such as 0012345 often stored as VARCHAR instead of INT?

Accepted Answer

C. It is an identifier whose leading zeros may be meaningful.

Answer

VARCHAR automatically checks that every phone number exists.

Answer

INT cannot store any positive whole numbers.

Answer

It is an identifier whose leading zeros may be meaningful.

Answer

VARCHAR automatically creates a foreign key to the telephone network.

Programming Concepts: Python and MySQL Practice MCQs

Programming Concepts: Python and MySQL Free MCQs

A company uses MySQL to store employee records in company_db. Which description correctly separates these terms?

A newly created table has six columns and no rows. What are its degree and cardinality?

Which statement about CREATE SCHEMA and CREATE DATABASE is correct in MySQL?

Each department has many employees, while each employee belongs to at most one department. Where should the department reference normally be stored?

An employee may have several independently managed phone numbers. Which design best represents this?

An order line is identified by an order ID together with a line number that repeats across orders. Which explanation fits?

Which declaration can identify an employee–project assignment without preventing either side from appearing in other assignments?

Which requirement distinguishes a candidate key from an arbitrary superkey?

A table declares PRIMARY KEY (employee_id, project_id). Which pair can be added when (101, 7) already exists, assuming both referenced parents exist?

Which statement about primary keys is correct?

An employee table allows department_id to be NULL and references department. Which insertion is valid, assuming all other column rules are satisfied?

Two employees belong to department 10. Must their department_id values differ?

Which type is most appropriate for an exact amount requiring two decimal places?

How many digits before the decimal point can DECIMAL(10,2) represent?

Why is a phone number such as 0012345 often stored as VARCHAR instead of INT?

Which practice remains safe across MySQL installations with different operating systems and configurations?

A nullable email column has UNIQUE. What happens when two different rows omit email and receive NULL?

A nullable status column has DEFAULT 'active'. An INSERT explicitly supplies NULL for status. What does the default alone require?

On modern MySQL with an enforced CHECK (salary >= 0), salary is nullable. Which input violates this check?

Why is a server version relevant when relying on a CHECK constraint?

After CREATE DATABASE company_db, which statement selects it for unqualified table names in the current connection?

Why is department created before employee in the worked design?

A table uses an integer primary key and a nullable foreign key. Which condition necessarily prevents inserting a new row?

Deleting department 10 succeeds under ON DELETE CASCADE. Which employees are affected by that referential action?

A design requires ON DELETE SET NULL on a department foreign key. Which column rule conflicts with that action?

A parent identifier changes under ON UPDATE CASCADE. What should happen to its matching child references?

Which statement is most useful for verifying the actual named foreign-key definition of employee?

CREATE TABLE employee_copy LIKE employee succeeds. Which conclusion is correct in MySQL?

The name column must allow 120 characters while remaining mandatory. Which command expresses this?

Adding UNIQUE(email) to an existing table fails because two non-NULL emails are identical. What explains the failure?

Which operation removes a column's stored values while retaining the employee table and its other columns?

Which statement about DROP TABLE IF EXISTS employee_copy is correct?

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