MySQL mcq questions and answers | MySQL MCQs

This question asks about a function in MySQL that gives you information about errors. Here's a breakdown of the options:
Option A: mysql_error() This function returns a string that contains the error message generated by the most recent MySQL operation. This is exactly what we are looking for!
Option B: mysql_errno() This function returns an integer value representing the error number of the most recent MySQL operation. This is not a textual error message.
Option C: mysql_sqlstate() This function returns a five-character string representing the SQLSTATE error code for the most recent MySQL operation. This is a standardized error code, not a full error message.
Option D: mysql_close() This function closes the connection to a MySQL server. It doesn't provide any information about errors.
Therefore, the answer is Option A: mysql_error().

This question asks about how the 'mysqlbackup' command works when you want to restore a MySQL database.
Let's break down the options:
Option A: copy-back-and-apply-log This means that the backup files are copied back to the original location, and then the transaction logs are applied to bring the database to the latest state.
Option B: apply-log-and-copy-back This option suggests that the transaction logs are applied first, and then the backup files are copied back.
Option C: copy-log-and-apply-back This option doesn't make sense in the context of database restoration. It suggests copying the log files and then applying them back to the original database.
Option D: apply-back-and-copy-log This option doesn't follow the standard restore procedure. It suggests applying the backup first, then copying the log files back.
The correct answer is Option A: copy-back-and-apply-log. This is the standard process for restoring a MySQL database using 'mysqlbackup' command. The backup files are restored first, and then the transaction logs are applied to ensure the database is updated to the latest state.

This question is about understanding how to use the "NOT IN" operator in MySQL to filter data. Let's break down what's happening:
* The Database: We have a database named "db_name" that stores information about interns. Each intern has a unique "intern_id" and a "subject" they are studying.
* The Data: * "intern_id" values are: 1, 2, 3, 4, 5, 6 * "subject" values are: sql, oop, sql, oop, c, c++
* One-to-One Relation: This means that each intern is associated with exactly one subject, and each subject is associated with exactly one intern.
* The SQL Statement:
```sql SELECT intern_id FROM db_name WHERE subject NOT IN (c, c++, oop); ```
This statement is asking us to:
1. SELECT the "intern_id" column.
2. FROM the database "db_name".
3. WHERE the "subject" column "NOT IN" the list of values: "c", "c++", or "oop".
* Finding the Answer:
Let's examine the data to see which "intern_id" values have subjects that are "NOT IN" the specified list:
* Intern 1: "subject" is "sql" - NOT in the list.
* Intern 2: "subject" is "oop" - IN the list (not selected).
* Intern 3: "subject" is "sql" - NOT in the list.
* Intern 4: "subject" is "oop" - IN the list (not selected).
* Intern 5: "subject" is "c" - IN the list (not selected).
* Intern 6: "subject" is "c++" - IN the list (not selected).
* Therefore, the correct answer is:
Option B: {1, 2, 3}
This is because the "intern_id" values 1 and 3 have subjects that are not "c", "c++", or "oop".

An Inequality Condition in MySQL refers to a comparison that checks if values are not equal. It's like saying "This is different from that."

Think of it like comparing two apples:
* Equal to: Both apples are the same size and color. * Not equal to: The apples are different sizes or colors.
In MySQL, we use symbols like != or <> to represent an inequality condition.

Let's look at the options:
* Option A: Not equal to - This is the correct answer. * Option B: Equal to - This is the opposite of an inequality condition. * Option C: Both Not equal to and Equal to - This is incorrect. Inequality conditions focus on "not equal to." * Option D: None of the mentioned - This is incorrect because Option A is the correct answer.
So, the answer is Option A: Not equal to.

This question is asking about the largest number you can store in a FLOAT data type in MySQL.

FLOAT is a data type used to store numbers with decimal points. It has a specific range of values it can hold.

The correct answer is Option A: 3.402823466E+38.

Let's break down why:

* E+38 means "multiplied by 10 to the power of 38". So, this number is a very large positive value.

* FLOAT in MySQL can handle a wide range of numbers, but it has limits on how big or small those numbers can be.

* The other options are either too small or too large to be within the valid range for FLOAT.

This question is asking about a special file that MySQL uses to store information about your database. Think of it like a list of important details about the database.
Let's look at the options:
Option A: db.otp - This doesn't sound like a file used by databases.
Option B: dp.zip - This might be a compressed file, but not a file used by MySQL to store database information.
Option C: db.opt - This looks like a file related to a database! It's a common name for files that hold database settings.
Option D: db.cls - This doesn't seem like a file associated with databases.
So, the most likely answer is Option C: db.opt.
Remember, the exact name might vary depending on your specific MySQL setup, but the idea is that the database attributes (like table names, column types, etc.) are stored in a file.

This question is asking about the part of the MySQL code that represents the search string.
Let's break down the code to understand it better:
* SELECT * FROM my_table - This part tells MySQL to retrieve all data from the table named "my_table".
* WHERE MATCH(abc) AGAINST('xyz'); - This part filters the results based on a full-text search. * MATCH(abc) - This specifies the column "abc" in the "my_table" to be searched. * AGAINST('xyz') - This defines the words or phrases to search for in the "abc" column. So, the "xyz" within the code represents the search string. It's the text that MySQL will look for in the "abc" column. Therefore, the correct answer is Option C: search string.

This question is asking about a type of join in MySQL. Joins are used to combine data from multiple tables based on a shared column.

Let's break down the options:

A. INNER JOIN: An INNER JOIN only returns rows where there is a match in both tables.
B. OUTER: This isn't a specific join type. It refers to LEFT OUTER JOIN or RIGHT OUTER JOIN, which include all rows from one table and matching rows from the other.
C. NATURAL: A NATURAL JOIN is similar to an INNER JOIN, but it automatically joins based on columns with the same name in both tables.
D. CARTESIAN: A CARTESIAN JOIN creates every possible combination of rows from both tables, even if there's no matching data. This can result in a very large result set!

The correct answer is D. CARTESIAN.

This MySQL command is used to filter rows from a table based on conditions related to "end_date", "title", and "start_date". Let's break down the command:
* WHERE end_date IS NULL: This part selects rows where the "end_date" column is NULL. It means that the value in the "end_date" column is empty or unknown.
* AND (title=’teller’ OR start_date < ‘2007-01-01’): This part uses the AND operator to combine two conditions. Let's further break down this part: * title=’teller’: This condition selects rows where the "title" column is equal to 'teller'. * OR start_date < ‘2007-01-01’: This condition selects rows where the "start_date" column is before '2007-01-01'.
In summary, the command will select rows that meet both conditions:
* The "end_date" must be NULL. * Either the "title" is 'teller', OR the "start_date" is before '2007-01-01'.
Therefore, the correct answer is Option D: All of the mentioned.
The command will select rows that meet any of these criteria:
* Employees with a NULL "end_date" and the title 'teller'. * Employees with a NULL "end_date" and a start date before '2007-01-01'.