MySQL mcq questions and answers | MySQL MCQs

This question is asking about a command in MySQL, which is a language used to manage databases.
We need to find the command that lists all the tables within a specific database.

Let's look at the options:
* SHOWS is not a valid command in MySQL.
* SHOWES is also not a valid command in MySQL.
* None of the mentioned might be tempting, but there is a correct answer.
* SHOW is the correct command! It's used to display various information in MySQL, including a list of tables.
So the answer is Option B: SHOW

This question is about how MySQL handles comparisons with NULL values. NULL represents the absence of data, so comparing it to anything, even a known value, is tricky.
Here's why the answer is Option A: null:
In MySQL, comparing a value to NULL using standard comparison operators like =, <, >, <=, >=, or != always results in NULL. This is because MySQL doesn't consider NULL to be equal to anything, not even itself.

Example:
```sql SELECT 5 = NULL; -- Output: NULL ```
To check if a value is NULL, you need to use the IS NULL operator.
Example:
```sql SELECT 5 IS NULL; -- Output: 0 (false) ```
Therefore, the correct answer is Option A: null.

This question asks about the 'SOCKET' protocol in MySQL and which operating systems it works with.
The 'SOCKET' protocol is a way for MySQL to communicate with other programs. It's like a bridge allowing them to share information.
Let's look at the options:
Option A: all This means the 'SOCKET' protocol works on every operating system, like Windows, Linux, macOS, etc.
Option B: unix only This means the 'SOCKET' protocol only works on Unix-based systems like Linux and macOS.
Option C: windows only This means the 'SOCKET' protocol only works on Windows operating systems.
Option D: none This means the 'SOCKET' protocol doesn't work on any operating systems.
The correct answer is Option A: all. The 'SOCKET' protocol is a common way for MySQL to connect and works on all major operating systems.

This question is about how MySQL's InnoDB storage engine makes sure that data relationships stay correct. Let's break down the options:
Option A: Atomicity - This means that a transaction (a set of changes) is either completely done or not done at all. It's like a bank transfer: either all the money moves, or none of it does.
Option B: Durability - This means that once a transaction is complete, the changes are permanent and will be saved, even if the database crashes. It's like writing something in stone – it's there to stay.
Option C: Consistency - This means that the database follows rules and constraints to ensure data accuracy. It's like making sure your math equations always add up correctly.
Option D: Referential Integrity - This is the key! It's a set of rules that guarantee relationships between tables are always valid. Imagine a table of students and a table of classes. Referential integrity ensures that every student in the "students" table has a valid matching class in the "classes" table.
So, the answer is Option D: referential integrity. It's the specific property that InnoDB uses to make sure those relationships are always valid.

This question asks if the given MySQL statement is valid. Let's break it down:
Understanding the SQL Statement:
* `SELECT abc, xyz FROM table1` This part selects the columns `abc` and `xyz` from the table `table1`. * `UNION` This keyword combines the results of two queries. It only includes unique rows from both datasets. * `abc, def FROM table2` This part seems to be trying to select columns `abc` and `def` from the table `table2`. However, it's missing the `SELECT` keyword, which makes it invalid.
Why the statement is incorrect:
The statement is incorrect because it's missing the `SELECT` keyword in the second part. To combine queries using `UNION`, both queries need to be complete `SELECT` statements.
The correct way to write the statement:
```sql SELECT abc, xyz FROM table1 UNION SELECT abc, def FROM table2; ```
Therefore, the answer is Option B: False.

In MySQL, a "VIEW" is like a special kind of shortcut. It lets you create a simplified way to look at data from one or more tables without actually changing the original tables.

Think of it like this: You have a big, complicated recipe book with many recipes. A VIEW is like a smaller recipe book that pulls together only the recipes you use most often, making it easier to find what you need.

Here's how VIEWS are helpful:

Option C: To simplify complexity of database design
- VIEWS can make complex queries easier to understand and use. You can create a VIEW that combines data from multiple tables in a way that makes sense for a specific task.
Option B: To hide the complexity of the database
- VIEWS can hide the underlying structure of the database from users. This is useful for security or for making the database easier to work with.
Option A: To hide columns from the users
- While you can choose which columns to include in a VIEW, it's not specifically about hiding columns.

Option D: All of the mentioned
- This is the best answer! VIEWS are designed to simplify database design, hide complexity, and provide easier ways to access specific data.

This question is about AUTO_INCREMENT in MySQL, which is used to automatically assign unique numbers to new rows in a table. Let's break down the scenario:
1. The last row has AUTO_INCREMENT value 32: This means the last row in the table was assigned the number 32.
2. A new row is added with AUTO_INCREMENT value 100: Normally, AUTO_INCREMENT would simply increment the last value, but you're manually setting it to 100.
3. The next row added will have value... Since you've overridden the automatic increment, the next row will pick up from the last manually assigned value.
Therefore, the correct answer is D: 101.

This question is about making a script file, called "run_me.sh," executable. This means the computer can understand and run the instructions inside the script.

The command used to make a file executable is "chmod +x filename".

Let's break down the parts:
* chmod: This is the command used to change file permissions. * +x: This adds the "execute" permission to the file. * filename: This is the name of the file you want to make executable (in this case, "run_me.sh").

So the correct answer is Option D: chmod +x run_me.sh

The other options are incorrect.
* Option A (chmod +e), Option B (chmod +a), and Option C (chmod +y) are not valid commands for changing file permissions in Linux or macOS.

This question is about how to set up tasks in MySQL that run automatically at specific times.
The options are different ways to describe the timing of these tasks:
Option A: EVERY - This is the correct answer! It's used to define tasks that happen repeatedly at fixed intervals. For example, "EVERY 10 minutes" or "EVERY hour".
Option B: ALL - This is not used for specifying intervals in MySQL.
Option C: AT - This is used for scheduling tasks to run at a specific point in time, like "AT 10:00 AM".
Option D: ALTERNATE - This is not used for scheduling tasks in MySQL.
So, if you want a task to run regularly, you'd use the "EVERY" clause to set the time between executions.

This question is asking about the AUTO_INCREMENT attribute in MySQL tables.
AUTO_INCREMENT is a special attribute that automatically assigns a unique, increasing number to each new row inserted into a table.
The question asks if only one column per table can have this attribute.
The answer is A: True.
In MySQL, you can only have one column per table with the AUTO_INCREMENT attribute. This is because the attribute is used to create a unique primary key for each row, and having multiple columns with this attribute could lead to conflicts.
So, the correct answer is Option A: True.