MySQL mcq questions and answers | MySQL MCQs

This question is asking about the size of a BIT data type in MySQL. A BIT data type is used to store a single bit of information, which can be either 0 or 1.

The size of a BIT data type is always 1 bit. It doesn't vary based on the value stored.

So the answer is Option A: 1.

This question is about how LOAD DATA works in MySQL.
LOAD DATA is a command that lets you import data into a table from a file.
LOCAL is a keyword you can use with LOAD DATA to tell MySQL to read the file from your local computer.
Without LOCAL, LOAD DATA reads the file from the server where MySQL is running.
So, the answer is Option B: less efficient.
Here's why:
- When you use LOCAL, MySQL can access the data directly from your computer, which is generally faster.
- Without LOCAL, MySQL has to transfer the data from the server, which adds extra time and makes the process slower.

This question asks about a MySQL variable that controls how table aliases are treated in terms of case sensitivity. Here's what you need to know:
* Table aliases are short names you can give to tables in your SQL queries to make them easier to refer to.
* Case sensitivity refers to whether uppercase and lowercase letters are treated differently. For example, "Table1" and "table1" are considered the same in a case-insensitive system, but different in a case-sensitive system.
The correct answer is Option A: lower_case_table_names.
Let's break down why:
* lower_case_table_names determines how MySQL stores table names internally. If this variable is set to 1 (the default), table names are stored in lowercase, and case sensitivity is ignored for table names and aliases.
* lower_case_all is a separate variable that controls case sensitivity for all identifiers (table names, column names, database names, etc.).
* lower_case_alias and lower_case_aliases are not valid MySQL variables.

This question is about MySQL Enterprise Backup, a tool that helps you create and manage backups of your MySQL database. It's asking where MySQL Enterprise Backup stores information about the backups it creates.
Let's break down the options:
* Option A: history_backup - This sounds like a plausible name for a table storing backup information.
* Option B: backup_history - This is another good possibility.
* Option C: backlog_history - "Backlog" usually refers to a queue of tasks. This doesn't seem directly related to backups.
* Option D: history_backlog - This combines the terms from Options A and C, making it less likely.
The most likely answer is either Option A or Option B. The actual table name might depend on the version of MySQL Enterprise Backup you're using.

This question asks about the best way to store money in a MySQL database. Let's break down the options:
Option A: INT
INT is for whole numbers. It wouldn't be good for storing money because money often has cents (like $10.50).
Option B: FLOAT
FLOAT is used for numbers with decimals. But it can have problems with precision. This means that sometimes tiny fractions of a cent might be lost, which is bad for financial calculations.
Option C: DOUBLE
DOUBLE is similar to FLOAT, but it can store even bigger and more precise numbers. Still, it might not be ideal for financial data.
Option D: DECIMAL
DECIMAL is the best option for storing money! It's specifically designed for storing numbers with a fixed number of decimal places, so you can be sure that every cent is accounted for.
So the answer is Option D: DECIMAL

This question is about the limits of data you can store in a single row of a MySQL table. Think of a row as a single entry in your database, like a single person's information in a contact list.

MySQL has a limit on how much data can fit in one of these rows. The question asks for the maximum size, meaning the largest possible amount of data.

Let's look at the options:

* Option A: 65534
* Option B: 65535
* Option C: 65536
* Option D: 65537

The correct answer is Option C: 65536. This means that the largest possible row in a MySQL table can hold 65,536 bytes of data.

Think of it like a box – the box can only hold so much stuff. In MySQL, the box is a row, and the "stuff" is the data you store.

This question is about foreign keys in MySQL. Foreign keys are used to connect different tables in a database. They ensure that data in one table is consistent with data in another.

The question asks whether foreign keys can handle deletes and updates.

Let's break it down:
- Deletes: When you delete a record in a table with a foreign key, MySQL can enforce the deletion. This means that if a record in the parent table is deleted, any related records in the child table will be deleted as well.
- Updates: Similarly, when you update a record in the parent table, MySQL can enforce the update. This means that if a value is changed in the parent table, the corresponding value in the child table will also be updated.

So, the answer to the question is False. Foreign keys can handle deletes and updates by enforcing consistency between tables.

This question is asking about how to set the SQL mode to TRADITIONAL in MySQL. The SQL mode determines how MySQL handles certain situations, like data types, syntax errors, and other aspects of your database.

The TRADITIONAL mode is a strict mode that follows the SQL standard closely, which can help catch potential errors and ensure your database behaves consistently.

To set the SQL mode to TRADITIONAL, you'll use a command-line option when starting MySQL.

The correct option is Option A: -sqlmode='TRADITIONAL'.

Let's break down why the other options are incorrect:

Option B: -sql_mode='TRADITIONAL': This option uses underscores (_) instead of hyphens (-) in the command. MySQL uses hyphens (-) for command-line options.

Option C: -sql-mode='TRADITIONAL': This option uses a hyphen (-) followed by a dash (-) in the command. The correct format is a single hyphen (-) before the option name.

Option D: -sql.mode='TRADITIONAL': This option uses a period (.) instead of a hyphen (-) in the command. MySQL uses hyphens (-) for command-line options.

In summary, the correct way to set the SQL mode to TRADITIONAL in MySQL is to use the command:

-sqlmode='TRADITIONAL'

This question asks if there's an error in a MySQL query. Let's break down the query and see if anything is wrong:
The Query:
```sql SELECT e.emp_id, e.fname, e.lname, d.name FROM employee AS e INNER JOIN department AS d ON e.dept_id = e.dept_id; ```
Explanation:
* SELECT: This part tells MySQL what data to retrieve. * e.emp_id, e.fname, e.lname, d.name: These are the columns we want to get. * FROM employee AS e INNER JOIN department AS d: This joins the `employee` and `department` tables. The `INNER JOIN` keeps only rows where the `dept_id` matches in both tables. * ON e.dept_id = e.dept_id: This is the JOIN condition – it specifies how the tables are connected.
The Error:
The error lies in the JOIN condition. It says `e.dept_id = e.dept_id`. This compares the `dept_id` column within the same table (`employee`)! You should compare `dept_id` in the `employee` table with `dept_id` in the `department` table for the join to work correctly.
Correct Join Condition:
```sql ON e.dept_id = d.dept_id ```
Answer:
Therefore, the answer is Option B: YES. There is an error in the MySQL statement.

This MySQL command retrieves data from the "employee" table. Let's break down the command:
SELECT *: This selects all columns (fields) from the "employee" table.
FROM employee: This specifies the table from which we want to retrieve data.
WHERE (title=’HEAD TELLER’) AND (start_date>2013-01-24): This is a filter that limits the results based on two conditions:
(title=’HEAD TELLER’): It selects only rows where the "title" column is exactly equal to 'HEAD TELLER'.
(start_date>2013-01-24): It selects only rows where the "start_date" column is greater than the date '2013-01-24'.

Therefore, the output will be:
Option B: All columns but only those rows which contain 'HEAD TELLER' as a "title" and start_date are greater than 2013-01-24
This command will fetch all columns from the "employee" table, but it will only include those rows that meet both criteria: their title is 'HEAD TELLER', and their start date is later than 2013-01-24.