MySQL Interview Questions and Answers
MYSQL is one of the most successful and leading pathways toward data administration careers. You will be amazed to know that this database service holds a total of 46.83% share in the relational database market. So to make your career and prepare for interviews in this field would be a good choice. Today we will help with these interviews by providing you with some MYSQL Interview Questions and Answers. MYSQL is one of the most popular database technologies used in the database industry. Popular companies like Microsoft, Amazon, Oracle, and IBM are using this technology on a vast basis to manage and store their data. According to one survey, nowadays more than 90% of organizations are using OSDBMS i.e. Open Source Database Management System. But to handle this database, professionals must know the MYSQL programming language.
| Quick Facts About MySQL | |
|---|---|
| What is the latest version of MySQL? | 8.0.22 released in 19th October 2020 |
| When was MySQL first released? | 23 May 1995 |
| Who developed MySQL? | Oracle Corporation. |
| What language does MySQL use? | C and C++ language |
| About License | GNU Public License |
| Official Website | https://www.mysql.com |
MySQL Query Interview Questions
Regex is an operational and powerful pattern that can help the users for the implementation of a powerful search utility function for database systems. Moreover, it is an operator which is used when we require matching regular expressions. In addition to this, it also supports a wider range of meta-characters which allow flexibility and more control over the database structure when performing pattern matching.
Match beginning of string(^):
SELECT name FROM users WHERE name REGEXP '^bestinterviewquestion';
UPDATE `your_table_name` SET new_field=old_field
| LENGTH() | CHAR_LENGTH() |
|---|---|
| It returns the total length of the string which is measured in bytes. | It returns the total length of the strings measured in characters. |
In MySQL, an ENUM is actually a string object whose value is selected from the list of permitted values pre-defined during the time of a column creation. It is used because it provides compact data storage in addition to readable queries and output.
Here’s the difference between an ENUM and a SET
| ENUM | SET |
|---|---|
| The value should be one listed in the column definition or internal numeric equivalent. | Must be an empty string consisting of values listed in column |
| mysql_fetch_array() | mysql_fetch_row() | mysql_fetch_object() |
|---|---|---|
| This returns an array of strings corresponding to a fetched row, or FALSE if there are no rows. | It returns with a numerical array of strings corresponding to a fetched row, or FALSE if there are no rows. | This returns with an object, or a FALSE value if there are no rows. |
| The returned array type depends on how result_type is defined | Here, the row is returned as an array. | This fetches a result row as an object type. |
Yes, the primary key can be dropped in MySQL with the use of the “ALTER TABLE” statement.
Syntax:
ALTER TABLE table_name DROP PRIMARY KEY
Images in MySQL can be stored as blobs. For saving them: All the database images are converted into the blobs first. Then, they will get inserted into the database, and later on, it will get stored into the disk.
To write an optimized query in MySQL, below are some guidelines:
- Functions should not be used in predicates.
- At the beginning of predicates, do not use the wildcard symbols such as %.
- Use only needed columns in the SELECT clause.
- Always use the inner join option.
- Use of the “Order by” clause is necessary for SQL, in case of assuming the sorted results.
In general slow query, the log is basically used in Mysql for the determination of which database queries will take a long duration to run. Moreover, a slow query log in MySQL simplifies that operations in the context of efficient and time-consuming queries.
In order to enable the slow query log the command- Get global slow_query_log – ‘ON’; is used
There are a number of unique features that are incorporated in Mysql 8 include-
- Unicode 9.0 support
- Window functions
- Recursive SQL syntax statements
- Support Native JSON data
- Support for document store Functionality
Conclusion
In MYSQL Database, data is stored in tabular form and that is why we also call it a Relational Database Management System. With the help of it, users can develop an infinite number of applications but it is mainly used for web applications. Talking about platforms, it can run on various platforms like LINUX, UNIX, and WINDOWS and is reliable, fast, and very easy to use. We hope these questions will help you to clear your core concepts regarding MYSQL. Let us help you with some short and important tips which might help you with your interviews-
- MYSQL is a programming language, so always avoid YES and NO answers.
- If you don’t know the answer, simply say I don't know rather than pretending you know.
- Always carry a pen and notepad with you.
- If you are stuck somewhere don’t panic, just stay calm and think out loud.
- Go with the expectation that you will reject a lot, as “Failure is the key to Success”.