MySQL Interview Questions and Answers

MySQL Interview Questions and Answers

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Best MySQL Interview Questions and Answers

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Q1) Define MySql

Answer: MySql, an open-source Database Management System.  MySql AB (assimilated by Oracle) is the one that constructed, maintained, and circulated MySql.

 Q2) List out the benefits of MySql

Answer: MySql has the below benefits:

• Opensource
• Consistent
• Quick
• Easy to use

Q3) When compared with Oracle, what are the advantages of MySql?

Answer: Below is the advantages of MySql when compared with Oracle:

• No charges involved as it an opensource tool
• Affords a GUI along with command prompt
• MySql is a portable
• MySql Query Browser takes care of the administration

Q4) Which command is used to add a row in a database?

Answer: INSERT is the command used to add a row.

Q5) Which command is used to remove rows from a table ‘SAMPLE’?

Answer: DELETE FROM SAMPLE WHERE …

Q6) Define SQL WHERE clause

Answer: SQL WHERE clause restricts the row data that are returned.

Q7) What is the major purpose of SQL?

Answer: To stipulate syntax and semantics of SQL data definition language, manipulation language and to describe the data structures.

Q8) What is a VIEW in SQL language?

Answer: The VIEW command is used to access a virtual table through SQL commands.

Q9) What command is used to remove a table from a database?

Answer: DROP TABLE is the command used to remove from a database.

Q10) Which is considered as an effective SQL query for an Index?

Answer: CREATE INDEX ID is the query used for an Index.

Q11) What are the string types used for columns?

Answer: The string types are,

• ENUM
• CHAR
• TEXT
• VARCHAR
• BLOB
• SET

Q12) How to login to MySql through Unix shell?

Answer: You can login using the below command,
# [MySql dir]/bin/MySql -h hostname -u <UserName> -p <password>

Q13) How to regulate the maximum size of a HEAP table?

Answer: The variable named ‘max_heap_table_size’ is used to control the size of a HEAP table.

Q14) Define federated tables

Answer: Federated table permits access to the tables that are available on other databases on different servers.

Q15) Mention different table types available in MySql

Answer: The table types are:

• Heap
• Merge
• MyISAM
• ISAM
• INNO DB

Q16) Define ISAM

Answer: ISAM (Indexed Sequential Access Method) was established by IBM to retrieve and store data on secondary storage systems.

Q17) What is the way to display the top 50 rows?

Answer: To display the top 50 rows, use the command given below:
SELECT * FROM
LIMIT, 0, 50;

Q18) Using CREATE command, what are the objects can be created

Answer: The objects are,

• DATABASE
• EVENT
• FUNCTION
• INDEX
• PROCEDURE
• TABLE
• TRIGGER
• USER
• VIEW

Q19) Mention the triggers used in MYSQL Table

Answer: The available triggers are,

• BEFORE INSERT
• AFTER INSERT
• BEFORE UPDATE
• AFTER UPDATE
• BEFORE DELETE and
• AFTER DELETE

Q20) What is a TEXT in MYSQL?

Answer: TEXT is said to be a case-insensitive BLOB. They are defined as a non-binary string. TEXT holds a character sets and values that are stored, and it is related based on the organization of the character set.

Q21) Mention the nonstandard string types

Answer: The Non-standard string types are,

• TINYTEXT
• TEXT
• MEDIUMTEXT
• LONGTEXT

Q22) What is BLOB?

Answer: BLOB defines a large binary object which is used to hold a flexible volume of data.

Q23) Mention the 4 types of BLOB in MYSQL

Answer: The available BLOB types are,

• TINYBLOB
• BLOB
• MEDIUMBLOB
• LONGBLOB

Q24) Mention one difference between temporary table and heap table

Answer: Temporary tables do not have the sharing options while the heap tables can be shared amount of different clients. Heap tables are considered as a storage point while a temporary one fails in storing the data.

Q25) Mention any 2 advantages of MYSQL to Oracle

Answer: The advantages are,

• MYSQL works great for database enabled items while Oracle is written for enterprises.
• MYSQL is portable and user-friendly.
• MYSQL consumes 1MB of RAM usage while Oracle uses more than 100 MB on your laptop.
  

Q26) Mention the query used to get current date in MYSQL

Answer: The query used to get the current date is,
SELECT CURRENT_DATE ();

Q27) Define save point concept in MySql

Answer: SAVEPOINT is defined as a statement in MySql to obtain a baptized transaction savepoint along with an identifier name.

Q28) List the column comparison operators used in MYSQL

Answer: The comparison operators are <<, <>, >=,>>, AND, LIKE, OR, <=, >, etc.

Q29) Which is the default port available in MYSQL?

Answer: 3306 is the default port allocated in MYSQL.

Q30) Define Primary key

Answer: To locate and identify a row in a table, a primary key is essentially used in the MySql server.
Q31) What is a candidate key?
Answer: A candidate key is defined as a set of columns that is majorly used to find any records in the MySql database without any need of a reference to data.

Q32) List the available drivers in the database

Answer: The available drivers in MYSQL are,

• PYTHON Driver
• JDBC Driver
• CAP11PHP Drive
• C WRAPPER
• ODBC Driver
• net5.mxz
• RUBY Driver
• PHP Driver
• PERL Driver

Q33) Define DML in MYSQL

Answer: Data Manipulative Language (DML) manages processes and data handlings. Few examples of DML commands include Insert and select.

Q34) Define DCL

Answer: Data Control Languages (DCL) is nothing but a permission concept. In other words, the approval to access various parts of a database.

Q35) What is the query used to concatenate strings?

Answer: To concatenate use the below query:
CONCAT (example string1, example string2, example string3)

Q36) Define foreign key

Answer: It is single or multiple columns that have values that are linked to a primary key to a different table.

Q37) Explain Index

Answer: Index is referred to 1 or many columns defined to have the values arranged uniquely manner to enhance data retrieval velocity.

Q38) Define rollback concept

Answer: Rollback concept helps to dismiss an operation or transaction while the database variations not protected to the MYSQL server.

Q39) Mention the groups of data types available in MYSQL

Answer: The three types are,

• Numeric
• Date & Time data
• String data types

Q40) Give a few examples of Numeric data types used in MYSQL

Answer: Numeric data types are,

• MEDIUMINT
• TINYINT
• BIGINT
• DOUBLE
• DECIMAL
• FLOAT
• BIT
• SMALLINT
• INTEGER

Q41) Give a few examples of String data types used in MYSQL

Answer: Available String data types are,

• VARCHAR
• LONGBLOB
• TEXT
• NVARCHAR
• BINARY
• CHAR
• TINYBLOB
• LONGBLOB
• ENUM
• MEDIUMBLOB
• TINYTEXT
• VARBINARY
• SET

Q42) Mention Time and Date data types available

Answer: Time and Date data types are,

• TIMESTAMP
• DATE,
• DATETIME,
• YEAR
• TIME

Q43) Give the SQL command to retrieve indexes from a table named ‘employee’

Answer: The command used to retrieve indexes from a given table is ‘SHOW INDEX FROM employee’.

Q44) Mention a way to drop existing View

Answer: The view can be deleted by using the command, ‘DROP VIEW viewName’.

Q45) Explain Data Warehousing

Answer: A Data Warehousing is simply defined as a central Data storehouse, formed using diverse Data Sources. 

Q46) List some common functionalities with MYSQL

Answer: The common functions used with MYSQL are,

• DATEDIFF
• CURRDATEO
• NOWO
• CONCAT

Q47) What is the numeric limit on indexed columns creation to a table?

Answer: 16 indexed columns can be created as a maximum limit.

Q48) How a user can get the current version of MYSQL application?

Answer: The syntax ‘SELECT VERSION ();’ is used to know the current version of MYSQL.

Q49) Mention the advantage of ENUM in a database

Answer: ENUM in MYSQL helps to condense the values/data that can enter a table.

Q50) Mention OLAP storage models available

Answer: The three models are,

• MOLAP
• HOLAP and
• ROLAP