MySQL mcq questions and answers | MySQL MCQs

This question is about getting data from a MySQL database using Perl's DBI module. Let's break down the options:
Option A: fetchrow_array()
This function retrieves a row from a result set and returns it as an array. Each element in the array corresponds to a column in the row.
Option B: fetchrow_arrayref()
This function is similar to fetchrow_array(), but it returns a reference to an array, which is a special way to point to the array without copying the entire array.
Option C: fetch()
This function retrieves the next row from a result set and returns it as a hash (like a dictionary). The keys of the hash are the column names.
Option D: fetchrow_hashref()
This function is similar to fetch(), but it returns a reference to a hash.
So, the function that returns a reference to an array of row values is fetchrow_arrayref().
Therefore, the correct answer is Option B.

This question asks about variables in MySQL, which are like special settings that control how MySQL behaves. We're looking for a variable that's read-only, meaning you can only see its value, you can't change it.
Let's break down the options:
Option A: error_count - This variable keeps track of how many errors MySQL has encountered. You can't change the number of errors, so this is a read-only variable.
Option B: big_tables - This variable is used for optimizing large tables, and its value can be changed.
Option C: autocommit - This variable controls whether changes are automatically saved (committed) after each query. You can change this setting.
Option D: foreign_key_checks - This variable controls whether MySQL checks for foreign key constraints (rules about how data is linked between tables). You can change this setting.
So, the answer is Option A: error_count.
This is because the number of errors is determined by the MySQL server itself, and you can't manually set it.

In MySQL, the BETWEEN keyword is used to select values within a specific range.

The BETWEEN operator needs two values: a lower limit and an upper limit.

Therefore, the correct answer is Option B: Lower and upper limit.

For example, if you want to select all rows where the age is between 18 and 30, you would use:

SELECT * FROM users WHERE age BETWEEN 18 AND 30;

This question asks if MySQL can run files that contain a series of commands, like a script. Think of a script as a list of instructions you give to a computer.
MySQL is a powerful database system, and it can definitely handle running these scripts.
So the answer is True.
MySQL uses special commands like SOURCE to run these script files.

This question is about how MySQL handles multiple commands you write in a single query.

Imagine you want to do several things at once, like:
1. Create a new table
2. Add some data to it
3. Update some of the data

You might try writing all three commands in one go, like this:
CREATE TABLE my_table (name VARCHAR(255)); INSERT INTO my_table (name) VALUES ('Alice'), ('Bob'); UPDATE my_table SET name = 'Charlie' WHERE name = 'Bob';

But by default, MySQL doesn't let you run all these commands at once. It expects each command to be separate.

So the answer is Option A: True.

You can enable multiple statement execution if you need it, but it's not the standard behaviour.

This question asks if you can tell what character set is being used just by looking at the collation name if the CHARACTER SET isn't explicitly mentioned.

Here's how it works:
* Character Set: Defines the set of characters a database can store. Think of it like a language dictionary.
* Collation: Determines how those characters are sorted, compared, and displayed. It's like the grammar rules of your language.
* Collation Name: Often includes the character set as part of the name. For example, `utf8_general_ci`.

So, the answer is True. The first part of a collation name usually tells you the character set.

For example, in `utf8_general_ci`, `utf8` is the character set.

This question tests your understanding of how MySQL handles numbers and hexadecimal values. Let's break it down:
* Hexadecimal Representation: The '0x' prefix tells us that '0x61' represents a hexadecimal number. Hexadecimal is a base-16 number system that uses digits 0-9 and letters A-F.
* Hexadecimal to Decimal: The hexadecimal value '0x61' is equivalent to the decimal number 97.
* Adding Zero: Adding zero to any number, regardless of the number system, always results in the original number.
Therefore, the correct answer is Option C: 97
In simpler terms, the question is asking you to convert the hexadecimal number '0x61' to its decimal equivalent, and then add zero to it.
Remember, MySQL interprets values with the '0x' prefix as hexadecimal.

This question is about how MySQL handles database selection.
The 'USE' command in MySQL is used to tell the database which database you want to work with.
The question asks if you need special permission (access privilege) to choose a database using 'USE'.

Think of it like opening a folder on your computer. You don't need special permission to open any folder, you can just click on it. Similarly, with 'USE' you can choose any database without special permission.

So the answer is True. You don't need access privileges to use the 'USE' command.