MySQL mcq questions and answers | MySQL MCQs

This MySQL command is used to retrieve information from a table called "employee".

Let's break down the command:
SELECT emp_id, fname, lname
This part tells MySQL which columns to display. It wants to show the emp_id, fname (first name), and lname (last name) from the table.
FROM employee
This part specifies the table from which to retrieve data.
WHERE title=’HEAD TELLER’ AND start_date>2008-11-23
This part acts like a filter. It only wants to include rows where the employee's "title" is "HEAD TELLER" AND their "start_date" is after 2008-11-23.

So, the output of this command will be:
Option C: Columns mention with "SELECT" clause and only those rows which contain 'HEAD TELLER' as a "title" and start_date>2008-11-23

In simpler terms, the command will show you the emp_id, fname, and lname for only those employees whose job title is "HEAD TELLER" and who started working after November 23rd, 2008.

This question asks about where data is stored and how quickly we can access it. Think of it like this:

Imagine your computer has two places to store things:

* Memory (RAM): This is like your computer's workspace, super fast but temporary. Think of it like a small, organized desk where you can quickly grab whatever you need.
* Disk (Hard drive/SSD): This is like a filing cabinet, slower but permanent. It holds all your data for long-term storage.

So, which is faster? Memory is much faster than disk! It's like the difference between grabbing a file from your desk vs. searching through a filing cabinet.

Therefore, the answer is Option A: memory.

This question is about foreign keys in MySQL. Foreign keys are used to ensure data integrity by creating a relationship between two tables. They make sure that the data in one table (the "referencing table") matches the data in another table (the "referenced table").

Think of it like this: You have a table called "Customers" and another called "Orders." In the "Orders" table, you have a column called "CustomerID." This column is a foreign key that references the "CustomerID" column in the "Customers" table. If you try to insert an order with a "CustomerID" that doesn't exist in the "Customers" table, MySQL will stop you!

Now, the question asks about a variable that controls whether this check is performed. The variable is called foreign_key_checks. When set to 1, this variable enables foreign key checking.

So the answer is Option C: foreign_key_checks

Let's look at why the other options are incorrect:

Option A: error_count - This variable keeps track of the number of errors that have occurred. It has nothing to do with foreign keys.

Option B: identity - This variable controls the behavior of auto-increment columns. It's not related to foreign keys.

Option D: autocommit - This variable determines whether changes are automatically committed to the database. It doesn't affect foreign key checking.

This question is about functions in MySQL used for connecting to a database.
Let's break down each function:
mysql_close(): This function closes the connection to the MySQL database. It doesn't return any value, it simply performs an action.
mysql_init(): This function initializes a MySQL connection handle. It also doesn't return any value; it prepares the connection handle for use.
mysql_real_connect(): This function establishes a connection to the MySQL database. It returns a value that indicates the success or failure of the connection attempt.
So, out of the three functions, two (mysql_close() and mysql_init()) do not return any value.
Therefore, the correct answer is Option C: 2.

This question is about MySQL and specifically how it handles delayed inserts. Delayed inserts are used when you want to add new rows to a table, but you don't want to slow down the current operation. Instead, the inserts are queued and executed later.

The question asks which system variable controls the size of the queue for delayed inserts per table. Here's the breakdown of the options:

Option A: fast_queue_size - This variable is not related to delayed inserts. It's used in other contexts.
Option B: general_queue_size - This variable also is not related to delayed inserts. It handles general query queues.
Option C: slow_queue_size - Like the others, this variable is unrelated to delayed inserts. It manages queries considered "slow."
Option D: delayed_queue_size - This is the correct answer. The delayed_queue_size system variable determines how many delayed INSERT statements can be queued per table before they start being rejected.

So the answer is Option D: delayed_queue_size.

This question is about how MySQL tells you if a query was successful or not.
The function `mysql_query()` is used to send SQL commands to the database.
When a command runs successfully, it returns a special value.
When something goes wrong, it returns a different value to signal an error.
The answer: Option C (-1).
So, if `mysql_query()` returns -1, it means your query failed.

This question asks about the number of values a stored procedure can return in MySQL.

Stored procedures are like mini-programs that you can run within your database. They can perform complex operations and return results.

Here's the breakdown:

* Option A: 0 - A stored procedure can definitely return no values. Imagine it just performs some tasks without sending back any data.
* Option B: 1 - It's possible for a stored procedure to return a single value, like a calculated total or a specific piece of information.
* Option C: 2 - Yes, stored procedures can return two or more values. This might be useful for getting multiple pieces of data in one go.
* Option D: 3 - Again, stored procedures are flexible, so they can return three or even more values.

The answer is: All of the above (A, B, C, and D). A stored procedure in MySQL can return any number of values, including zero.

This question is about the DISTINCT keyword in MySQL.
The DISTINCT keyword is used to remove duplicate values from the result set of a query.
In this case, we are selecting the cust_id column from the "account" table using the following query:

SELECT DISTINCT cust_id
FROM account;

The cust_id column has the following values: {1, 2, 2, 3, 3, 5, 6, 7, 8, 8}.
Since we are using the DISTINCT keyword, the query will only return the unique values from the cust_id column.
Therefore, the output of the query will be: {1, 2, 3, 5, 6, 7, 8}.
So the correct answer is Option B.

This question asks you about the meaning of UTF in the term utf8. UTF is a standard used for representing characters from different languages in computers.
Let's break down the options:
Option A: Universal Transformation Format
Option B: Unicode Transformation Format
Option C: Universal Transformation Formula
Option D: Unicode Transformation Formula
The correct answer is Option B: Unicode Transformation Format.
Explanation:
UTF stands for Unicode Transformation Format. It's a way of encoding characters using a standard called Unicode.
Unicode is a system that assigns a unique number to every character, regardless of the language it's from.
utf8 is a specific implementation of UTF. It's a popular encoding scheme that uses 8-bit units (bytes) to represent characters.
So, when you see utf8 in MySQL, it means that the database is using the Unicode Transformation Format (UTF) to store and display characters from various languages.

This question is asking about the MySQL binary protocol and how it handles different SQL statements.
The binary protocol is a way for MySQL clients to communicate with the server. It's more efficient than the text protocol, but it doesn't support every single SQL statement.
So the answer is Option A: True
Explanation:
The binary protocol is designed to be fast and efficient, but it has limitations. It doesn't support all SQL statements, especially some more complex or rarely used statements.
If you try to execute a statement that the binary protocol doesn't support, you might get an error.