MySQL mcq questions and answers | MySQL MCQs

This question is asking about a special word you can use in MySQL to see information about the current connection you are using. This information might include things like what database you are connected to, what your user permissions are, and how long you've been connected.
The keyword you need to use is SESSION.
Let's break down why the other options aren't correct:
GLOBAL - This keyword shows information about the entire MySQL server, not just your current connection.
LOCAL - This keyword is not used with the SHOW STATUS statement.
DEFAULT - This keyword isn't related to the SHOW STATUS statement.
So the answer is Option B: SESSION.

Imagine you have a table called "products" with columns like "product_id", "product_name", and "price". You want to display the price of each product, but you want to call it "cost" in your results instead of "price".
This is where column aliases come in handy.
Column aliases let you assign new names to the columns in your SELECT statement's results.
So, the answer is Option D: All of the mentioned.
Let's break down the options:
Option A: This is correct. Column aliases let you give your columns new labels in the result set.
Option B: This is also correct. Column aliases can overwrite existing column names.
Option C: This is also correct. Column aliases are useful when you're working with literals, expressions, or built-in functions in your SELECT clause.
In short, column aliases give you more control over how your query results are displayed.

This question asks about deleting rows from a table using a DELETE statement in MySQL. Let's break it down:
1. DELETE Statement:
The `DELETE` statement is used to remove rows from a table. It follows the syntax:
`DELETE FROM table_name WHERE condition;`
2. The `WHERE` Clause:
The `WHERE` clause specifies which rows to delete based on a condition. In this case, the condition is `person_id < 10`. This means we're targeting rows where the `person_id` column is less than 10.
3. Primary Key:
The question mentions that `person_id` is a primary key. A primary key in a table ensures that each row has a unique identifier. It cannot have duplicate values.
4. Understanding the Logic:
Since `person_id` is a primary key, it cannot have duplicate values. This means that any value less than 10 in `person_id` will be unique.
5. Answer:
Therefore, the `DELETE` statement will delete all rows where `person_id` is less than 10. The correct answer is Option A: 0-9.
In simpler terms:
The command will remove all the rows with `person_id` from 0 to 9, as it's a primary key and there cannot be duplicates.

This MySQL statement uses an equality condition.

Let's break it down:

* SELECT fname FROM person : This part tells MySQL to retrieve the "fname" (first name) column from the "person" table.
* WHERE fed_id='111-11-111'; : This is the important part! The WHERE clause filters the data. We're looking for rows where the "fed_id" column is equal to '111-11-111'. That's an equality comparison.

Here's why the other options are incorrect:
* Inequality condition: An inequality condition would use operators like != (not equal), < (less than), > (greater than), etc.
* Range condition: A range condition would use operators like BETWEEN to specify a range of values.

Therefore, the correct answer is Option A: Equality condition.

This question asks about the fetchrow_hashref() function in MySQL. This function is used to get a row of data from a result set and store it as a hash, which is like a special kind of list where each item has a unique key.

The question wants to know what these keys are. The answer is column names.

Here's a simple explanation:
Imagine a table in your database with columns named "Name", "Age", and "City". When you use fetchrow_hashref(), it returns a hash where:
* The keys are "Name", "Age", and "City" (the column names).
* The values are the actual data from that row (like "John", "30", "New York").

So, the correct answer is Option B: column name.

This question is about how MySQL handles table aliases, which are short names you can give to tables to make your SQL queries easier to read.
Let's break down the options:
Option A: lower_case_table_names This variable controls whether MySQL stores table names in lowercase. It doesn't directly affect aliases.
Option B: lower_case_all This variable controls whether MySQL converts all identifiers (including table names, column names, and aliases) to lowercase.
Option C: lower_case_alias This option isn't a real MySQL variable.
Option D: lower_case_aliases This option isn't a real MySQL variable.
The correct answer is Option B: lower_case_all. If you set this variable to 1, MySQL will treat all identifiers (including table aliases) as case-insensitive. For example, if you have a table named `Customers` and you use the alias `customers` in your query, it will work as expected.

This question asks about finding words in a database using natural language. Imagine you're searching for a book in a library. You could look for the exact title, or you could use words related to the book's topic to find it.

In MySQL, we have special keywords for this kind of search. The keyword that lets you search for words in natural language is MATCH.

Let's look at the options:
* MATCH: This keyword is used with AGAINST to perform a full-text search.
* AGAINST: This keyword works together with MATCH to specify the text you're searching for.
* SEARCH: This isn't used for full-text searches in MySQL.
* FIND: This is used to find a specific string within another string, but not for full-text searches.

So, the answer is Option A: MATCH. It's part of a pair with AGAINST for searching through words naturally.

This question is asking about the meaning of the word "xyz" in the given SQL statement.

The statement uses the UNION operator, which combines the results of two SELECT queries.

In the first query, "SELECT xyz FROM table1", "xyz" is what we are selecting. This means "xyz" must be a name that identifies something within the table.

The options are:
* Option A: row name - Rows are not named in SQL.
* Option B: column name - This is the most likely answer. Columns are named and hold specific data within a table.
* Option C: table name - Table names are used to specify which table to use in the query, and are not used within the SELECT statement.
* Option D: database name - Database names are used to specify which database the tables are in, and are not used within the SELECT statement.

Therefore, the correct answer is Option B: column name.

This question asks about a function in MySQL that helps you get data from a database query and organize it into an array.

Think of it like this:
You ask MySQL a question (your query), and it gives you a bunch of answers (the rows of data).
The function you need helps you gather those answers and put them in a structured way so you can easily work with them.

Let's break down the options:
Option A: fetchrow_array() This is the correct answer! It grabs a single row of data and puts it into an array, so you can access each piece of information individually.
Option B: fetchrow_arrayref() This is similar to Option A, but it uses a special type of array called a "reference" which lets you change the original data.
Option C: fetch() This function is a more general way to get data, but it doesn't necessarily put it into an array format.
Option D: fetchrow_hashref() This function works with a special type of array called a "hash", which uses unique keys to access data. It's like having a dictionary where you can look up values using their names.

In short: The function you're looking for is fetchrow_array() because it gives you a single row of data in a simple, easy-to-use array format.

This question asks about how to get rid of indexes on a table in MySQL. Indexes help your database find information quickly, but sometimes you might need to remove them.

Let's look at the options:

Option A: DROP INDEX - This is the correct answer! You use `DROP INDEX` to delete an index from a table.

Option B: DELETE INDEX - This is incorrect. `DELETE` is used to remove rows from a table, not indexes.

Option C: REMOVE INDEX - This is also incorrect. MySQL doesn't have a command called `REMOVE INDEX`.

Option D: FLUSH INDEX - This is incorrect. `FLUSH INDEX` is used to refresh the index cache, not delete indexes.

So, the answer is Option A: DROP INDEX.