MySQL mcq questions and answers | MySQL MCQs

This question is asking about what the code does in MySQL. Let's break it down:
SELECT * FROM table_1;
* SELECT: This tells the database you want to get data from the table. * *: This means you want to get all the data from the table. * FROM: This tells the database which table to get the data from. * table_1: This is the name of the table.
So, what does this code do? It retrieves all the data (all columns) from the table named 'table_1'.
Here's what the answer choices mean:
Option A: invalid: This is incorrect. The statement is a valid SQL statement.
Option B: display contents of table_1: This is the correct answer. The code will display all the rows and columns in the table.
Option C: improper case being used: While it's good practice to use lowercase for SQL keywords, this statement is valid even with uppercase.
Option D: display only column names in table_1: This is incorrect. The code will display all the data, not just the column names.
Let me know if you'd like any more explanation!

Imagine you have two tables, one for students and another for courses.
Each student can enroll in multiple courses, and each course can have many students.

To connect these tables, we use a special kind of key called a foreign key.
The foreign key in the students table points to the primary key in the courses table.

This way, we can easily find the courses a specific student is enrolled in or the students taking a specific course.

So the answer is Option C: foreign

This question asks about how SBR replication works in MySQL. SBR stands for Statement-Based Replication.

Let's break down the options:

* Option A: Statement based - This is the correct answer. SBR replication copies SQL statements from the master server to the slave server. The slave server executes these statements to keep its data in sync with the master server.

* Option B: Row based - This refers to Row-Based Replication (RBR), a different type of replication in MySQL. RBR copies changes to individual rows, not entire statements.

* Option C: Column based - MySQL doesn't have a replication method that works solely on a column basis.

* Option D: Table based - There's no specific "table-based" replication in MySQL. Replication generally focuses on rows or statements.

In summary, SBR replication is Statement-Based Replication, which means it replicates SQL statements to keep the slave server synchronized with the master server.

This question is about cardinality in MySQL. Cardinality measures how many unique values are present in a column.

Imagine a column with these values:
Apple, Orange, Apple, Banana, Pear, Orange, Grape

We have 7 values in total, but only 6 unique values (Apple, Orange, Banana, Pear, Grape).

So, the cardinality is 6.

Therefore, the correct answer is Option B: 6.

This question is about the limits of how long a database name can be in MySQL.
MySQL has rules about how long names can be for different things, like tables, columns, and databases.
In this case, we want to know the maximum length allowed for a database name.
Think of a database as a big container where you store information.
Each database can have different tables and data inside.
Let's look at the options:
Option A: 16 - This is too short, database names can be longer.
Option B: 32 - This is also too short.
Option C: 64 - This is still too short.
Option D: 128 - This is the correct answer! In MySQL, you can have database names up to 128 characters long.
So, the maximum number of characters allowed for a database name in MySQL is 128.

This question is asking about the best data type to store a large number in a MySQL database.
Let's break down the options:
TINYINT can store small numbers from -128 to 127.
SMALLINT stores numbers from -32,768 to 32,767.
MEDIUMINT stores numbers from -8,388,608 to 8,388,607.
BIGINT stores numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

Since we need to store values up to 2 million, BIGINT is the best choice because it can handle the largest range of numbers.

Answer: D) BIGINT

This question asks you to identify which line of code will cause an error when running in a MySQL database. Let's break down each option:
Option A: SELECT * FROM person WHERE person_id=1;
This statement is a standard way to retrieve all data (*) from a table named "person" where the "person_id" column equals 1. This is a valid SQL query and will not produce an error.
Option B: SELECT pname FROM person;
This statement retrieves only the "pname" (presumably "person name") column from the "person" table. This is a valid SQL query and will not produce an error.
Option C: SELECT pname, lname, person_id FROM person;
This statement retrieves multiple columns ("pname", "lname", and "person_id") from the "person" table. This is a valid SQL query and will not produce an error.
Option D: None of the mentioned
Since options A, B, and C are all valid SQL queries, the correct answer is Option D: None of the mentioned.

This question is about the FLOAT data type in MySQL, which is used to store numbers with decimal points.

FLOAT has a maximum value it can hold. We need to find the largest possible non-zero number a FLOAT can represent.

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

This number is represented in scientific notation, which is a shorthand way to write very large or very small numbers. 'E+38' means you multiply the number by 10 raised to the power of 38.

The other options are incorrect because they are either too small or too large for the maximum value of a FLOAT in MySQL.

This question asks about a special feature in MySQL that lets you use double quotes (") to write names for things like tables and columns.
Normally, in MySQL, you use backticks (`) to write these names. But, there is a way to change this behavior.
The correct answer is Option B: ANSI_QUOTES.
This setting tells MySQL to follow a standard called "ANSI SQL", which allows you to use double quotes for names.
Let's look at the other options:
Option A: ANSI is related to standards, but it doesn't specifically deal with double quotes for identifiers.
Option C: TRADITIONAL is a mode that enforces stricter rules, making it less likely to allow double quotes for names.
Option D: PIPES_AS_CONCAT is a mode that lets you use pipes (|) to join strings together. It's not related to identifiers.
So, the ANSI_QUOTES mode is the only option that lets you use double quotes for identifier names.

The slow query log in MySQL is like a detective's notebook.
It keeps track of queries that take a long time to complete.
This helps us identify queries that might be slowing down our database.
So, the answer is True.
The slow query log is a valuable tool for identifying performance issues.