MySQL mcq questions and answers | MySQL MCQs

This question is about the `fetchrow_hashref()` function in MySQL. This function is used to retrieve data from a database and store it in a special data structure called a hash.

Imagine a hash as a container where you store information. Each piece of information has a unique label (like a name tag) that helps you find it quickly. In the case of `fetchrow_hashref()`, the labels are the column names of the table you are querying.

So, when you use `fetchrow_hashref()`, the function will return a hash where each row's data is stored. You can access this data using the corresponding column names as keys.

Therefore, the correct answer is Option B: column name.

This question is asking about a file type used in MySQL to run multiple commands. Here's how to understand the options:
Option A: makefile
A Makefile is used in software development to organize the building of a project, but it's not specific to MySQL.
Option B: dofile
The dofile command in MySQL allows you to run commands from a file. This is the correct answer.
Option C: putfile
The putfile command is used to transfer data from a client to a server, not to execute commands.
Option D: pushfile
There is no pushfile command in MySQL.
Therefore, the correct answer is Option B: dofile

This question asks if we can write hexadecimal numbers in a special way called "scientific notation."

Here's the breakdown:
* Hexadecimal Numbers: These are numbers written using base 16, using digits from 0 to 9 and letters A to F.
* Scientific Notation: This is a way to write very large or very small numbers in a compact way. It uses powers of 10.

For example:
* The hexadecimal number 0x10 is equivalent to 16 in decimal.
* The decimal number 123456789 can be written in scientific notation as 1.23456789 x 10^8.

Now, can we write a hexadecimal number like 0x10 in scientific notation?

The answer is False.

We don't use scientific notation for hexadecimal numbers. We use them for decimal numbers to represent very large or very small values.

Therefore, the correct option is B: False.

This question asks about Views in MySQL.
A View is like a saved query that allows you to see only specific parts of a table, like a filtered window into your data.
So, can a View be used to pick and choose only certain columns from a table?
The answer is True.
Views are very helpful for:
- Simplifying complex queries.
- Limiting access to sensitive data.
- Making your database structure more user-friendly.
Think of a view as a custom snapshot of your data that shows you only what you need to see!

This question is about starting a transaction in MySQL. Transactions are a way to group multiple SQL statements together so they are treated as one unit. If all the statements in a transaction are successful, the changes are committed to the database. But if any statement fails, all the changes are rolled back.

The command to disable autocommit and launch a transaction is START TRANSACTION.

Here's why the other options are incorrect:

INITIATE TRANSACTION is not a valid MySQL command.
DISABLE AUTOCOMMIT only disables autocommit, but it doesn't start a transaction.
TRANSACTION is not a command but a keyword used in other commands.
Therefore, the correct answer is Option B: START TRANSACTION

This question asks about the way to define a "Constraint Check" in MySQL. A constraint check is like a rule that makes sure the data you put into a table is correct.
Let's break down the options:
Option A: gender char(1) check( gender IN ('M', 'F'))
This is the correct syntax!
* gender char(1) defines a column named "gender" that can store a single character (like 'M' or 'F').
* check( gender IN ('M', 'F')) is the constraint check. It ensures that the value entered in the "gender" column must be either 'M' or 'F'.
Option B: gender char (1) check
This is incorrect. It's missing the condition inside the parentheses that defines the check.
Option C: gender char (1) check ( gender )
This is also incorrect. The condition "gender" isn't enough to define a proper check. It needs to specify what values are allowed.
Option D: none of the mentioned
Since Option A is correct, this is incorrect.
In summary, Option A is the right way to define a "Constraint Check" in MySQL. It makes sure that the data entered into the "gender" column follows the specific rules defined by the check.

This question is about how you interact with objects in PHP, a popular programming language used for web development. Think of an object as a container that holds different pieces of information (like a person's name, age, or address).
To access these pieces of information, called properties, you use an operator. The operator is like a special symbol that tells PHP what you want to do.
Here's what each option means:
Option A: . This operator is used for accessing properties of classes. Classes are like blueprints for creating objects.
Option B: * This operator is used for multiplication in PHP.
Option C: -> This is the correct answer! The -> operator is used to access properties and methods of an object.
Option D: @ This operator is used for error control in PHP. It silences errors.
So, if you want to get the name of a person object, you would use the -> operator like this:
$person->name
This code would retrieve the value of the name property from the $person object.

This question is about how MySQL stores data from a table. When you retrieve data from a MySQL database, it needs to be organized in a way that your code can understand.
Think of it like a box that holds information. Each item in the box represents a row from your table.
The question asks about a special kind of box called a non-handle array. This box holds information as a simple list of values, like "Name", "Age", "City". Each value is in the list, but there's no special key to connect them back to the column names.
Of the options, the one that is most likely used to represent this non-handle array is $rv (Option B).
Think of $rv as the box that contains the row of data you requested from your MySQL database.
$rc (Option A) is usually associated with the number of rows affected by a query (like how many rows were updated or deleted), so it's not the right answer.
$rows (Option C) is often used to hold a collection of rows, not just one. It's like a box that holds multiple boxes of data.
$ary (Option D) is a general term for an array, which is a flexible data structure. While it could potentially hold a non-handle array, it's not specifically used by MySQL for that purpose.
Therefore, the correct answer is Option B: $rv

This question is about how MySQL orders data. We have a set of employee IDs (emp_id) {1, 2, 3, 4, 1, 1} in a table called person.
The SQL statement SELECT emp_id FROM person ORDER BY emp_id; tells MySQL to:
1. Select the employee IDs (emp_id)
2. From the table called person
3. Order them by the employee ID, from smallest to largest.
Therefore, the correct output is Option A: {1, 1, 1, 2, 3, 4} because the statement sorts the IDs in ascending order.
The duplicates (1, 1, 1) are not removed by the ORDER BY clause, they just appear in the order based on their numerical value.

This question asks about a special code used in MySQL to represent a carriage return.
A carriage return is like pressing the "Enter" key on your keyboard. It moves the cursor to the beginning of the next line.

Let's look at the options:
Option A: 'c' - This is not the escape sequence for carriage return.
Option B: 'r' - This is the correct answer! 'r' represents a carriage return in MySQL.
Option C: 'b' - This escape sequence represents a backspace, not a carriage return.
Option D: 'z' - This escape sequence represents the end of a string in MySQL, not a carriage return.

So the answer is Option B: 'r'