MySQL mcq questions and answers | MySQL MCQs

This question asks about where it's faster to get data: from memory or from disk?

Think of it like this:
- Memory is like your desk where you keep the things you're currently working on. It's fast to grab something from your desk.
- Disk is like a filing cabinet where you store lots of information. It takes longer to find something in a filing cabinet.

So, which is faster? Memory is much faster than disk!

Therefore, the answer is Option A: memory

This question asks about a column attribute in MySQL that helps assign unique numbers for identification. Let's break down the options:
Option A: AUTO_INCREMENT: This is the correct answer! AUTO_INCREMENT automatically generates a unique number for each new row added to the table. It starts with a specific value and increases by one for each new entry.
Option B: UNSIGNED: This attribute specifies that a column can only hold positive numbers (no negative values). While it helps with data consistency, it doesn't directly provide unique identification numbers.
Option C: IDENTIFY: MySQL doesn't have an attribute called "IDENTIFY."
Option D: DESCRIBE: DESCRIBE is a command used to get information about a table's structure, not a column attribute itself.
Therefore, the answer is Option A: AUTO_INCREMENT. It's the attribute responsible for generating unique numbers for identification in MySQL tables.

This question is about how MySQL connects to your computer on Windows.
Shared memory is a way for different parts of a program to communicate quickly and easily by using a special area in the computer's memory.
MySQL is a popular database system, like a digital filing cabinet for your information.
So, the question asks:
Does MySQL on Windows use shared memory to connect to your programs?
Let's look at the options:
Option A: True
Option B: False
The correct answer is Option A: True. MySQL on Windows does use shared memory for connections. It's a fast and efficient way for MySQL to communicate with other programs on your computer.

This question is about Data Definition Language (DDL) in MySQL. DDL commands are used to define and manage the structure of your database.

SELECT, FROM, and WHERE are all part of Data Manipulation Language (DML), not DDL. DML commands are used to manipulate the data within your database.

Here's a breakdown of each option:

Option A: SELECT - This command is used to retrieve data from your database. It's a DML command.
Option B: FROM - This clause is used in conjunction with SELECT to specify which table to retrieve data from. It's also a DML command.
Option C: WHERE - This clause is used in conjunction with SELECT to filter the data retrieved. It's also a DML command.

Therefore, the correct answer is none of the above.

Examples of DDL commands include:
* CREATE TABLE - Creates a new table in your database.
* ALTER TABLE - Modifies the structure of an existing table.
* DROP TABLE - Deletes a table from your database.

Remember, DDL commands are for defining the structure of your database, while DML commands are for working with the data inside it.

This question is about different types of subqueries in MySQL. Let's break it down:
Subqueries are queries within other queries. They are used to fetch data that is then used in the main query.
Correlated Subqueries depend on the outer query. They can't be executed alone because they need information from the main query to work. Think of them as helper queries that need a specific context.
Uncorrelated Subqueries are independent. They can be executed on their own because they don't rely on any external information.
EXISTS and NOT EXISTS subqueries check if certain data exists in a table. They can also be run independently.
So, the answer is Option A: Correlated
Correlated subqueries cannot be executed independently because they rely on data from the outer query. They are like little assistants that need the main query's instructions to work.

This question asks about ways to write comments in MySQL. Comments are like notes in your code that the computer ignores. They help you explain what your code does, making it easier to understand.

Let's look at the options:

Option A: #
This is a valid way to write a comment in MySQL. Anything after the '#' symbol on the same line is ignored by the database.

Option B: /* */
This is another way to write comments. You can put comments between the '/*' and '*/' symbols. This allows for multi-line comments.

Option C: —
This is a valid way to write a comment in MySQL. Anything after the '--' symbols on the same line is ignored by the database.

Option D: !#
This is NOT a valid way to write a comment in MySQL. MySQL doesn't recognize '#!' as a comment symbol.

Therefore, the answer is Option D: !#

This question is asking about the default storage engine used by MySQL. A storage engine is responsible for how MySQL stores and manages your data.

Think of it like a filing system for your data. Different storage engines organize the data differently.

The question wants to know which storage engine is automatically used if you don't specify one when you create a table.

Let's look at the options:

Option A: EXAMPLE - This isn't a real MySQL storage engine.
Option B: ARCHIVE - This is a storage engine, but it's not the default.
Option C: MyISAM - This was the default storage engine in older versions of MySQL.
Option D: NDB - This is a storage engine designed for distributed databases, not the default.

The correct answer is Option C: MyISAM. While MyISAM isn't the default anymore in newer MySQL versions, it was for a long time.

Important Note: In modern MySQL versions, the default storage engine is usually InnoDB, but the question is likely referring to older versions where MyISAM was the standard.

This question is asking about the rules for naming things in SQL, like tables and columns.
SQL has specific rules for naming things. One important rule is that you can't use just any character.
Let's look at the options:
Option A: . (period) Periods are used to separate parts of a name, like database names from table names. They are not allowed as part of the actual name itself.
Option B: _ (underscore) Underscores are perfectly fine to use in names! They are commonly used to make names more readable, like "customer_name".
Option C: $ (dollar sign) Dollar signs are not allowed in unquoted identifier names. They are used for something else in SQL.
Option D: 2 (number) Numbers are allowed in names, but only if they are not the first character. So, "table2" is fine, but "2table" is not.
The answer is Option A: . (period).

This question asks about the meaning of "xyz" in a MySQL statement. Let's break it down:
The statement is:
CREATE VIEW xyz AS SELECT a, b FROM t;
This statement is creating a view in MySQL.
A view is like a virtual table that doesn't store data directly, but instead gets its data from another table. In this statement, "xyz" is the name of the view being created.
So the correct answer is Option C: view.

This question is about different data types in MySQL and how they behave when you update data.
Let's break down each option:
* Option A: DATE - Stores a date (like '2023-12-18'). Updating a DATE value is simple; you just change the date. * Option B: TIME - Stores a time (like '10:30:00'). Similar to DATE, updating TIME involves changing the time value. * Option C: TIMESTAMP - Stores a timestamp (a combined date and time). This is the special one! Whenever you insert a new row or update a row in a table, MySQL automatically sets the TIMESTAMP column to the current date and time. You don't need to manually update it. * Option D: YEAR - Stores a year (like 2023). Updating a YEAR value is straightforward; you change the year.
So, the answer is Option C: TIMESTAMP.
This is because it has a special automatic update behavior, while the other options do not.