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Home Questions & Answer Technology Questions & Answers MySQL Questions & Answers

MySQL Questions & Answers (Compiled from UPSC, SSC ,PSC ,IBPS previous question papers)

  • What are the disadvantages of MySQL

  • A
    1. MySQL is not so efficient for large scale databases.
    2. It does not support COMMIT and STORED PROCEDURES functions version less than 5.0.
    3. Transactions are not handled very efficiently.

  • What are the drivers in MySQL

  • A

    Following are the drivers available in MySQL:

    • PHP Driver
    • JDBC Driver
    • ODBC Driver
    • C WRAPPER
    • PYTHON Driver
    • PERL Driver
    • RUBY Driver
    • CAP11PHP Driver
    • Ado.net5.mxj

  • What are the advantages of MySQL in comparison to Oracle?

  • A
    1. MySQL is a free, fast, reliable, open source relational database while Oracle is expensive, although they have provided Oracle free edition to attract MySQL users.
    2. MySQL uses only just under 1 MB of RAM on your laptop while Oracle 9i installation uses 128 MB.
    3. MySQL is great for database enabled websites while Oracle is made for enterprises.
    4. MySQL is portable.

  • What is the difference between heap table and temporary table

  • A

    Heap tables:

    Heap tables are found in memory. They are used for high speed storage on temporary basis. They do not allow BLOB or TEXT fields.

    Heap tables do not support AUTO_INCREMENT.

    Indexes should be NOT NULL.

    Temporary tables:

    The temporary tables are used to keep the temporary data. Sometimes it is very useful in cases to keep temporary data. Temporary table is deleted after current client session terminates.

    Main differences:

    The heap tables are shared among clients while temporary tables are not shared.

    Heap tables are just another storage engine, while for temporary tables you need a special privilege (create temporary table).

  • Define REGEXP?

  • AREGEXP is a pattern match in which matches pattern anywhere in the search value.

  • What is BLOB and TEXT in MySQL?

  • A

    BLOB is an acronym stands for binary large object. It is used to hold a variable amount of data.

    There are four types of BLOB.

    1. TINYBLOB
    2. BLOB
    3. MEDIUMBLOB
    4. LONGBLOB

    The differences among all these are the maximum length of values they can hold.

    TEXT is case-insensitive BLOB. TEXT values are non-binary strings (character string). They have a character set and values are stored and compared based on the collation of the character set.

    There are four types of TEXT.

    1. TINYTEXT
    2. TEXT
    3. MEDIUMTEXT
    4. LONGTEXT
  • Explanation:

    BLOB is an acronym stands for binary large object. It is used to hold a variable amount of data.

    There are four types of BLOB.

    1. TINYBLOB
    2. BLOB
    3. MEDIUMBLOB
    4. LONGBLOB

    The differences among all these are the maximum length of values they can hold.

    TEXT is case-insensitive BLOB. TEXT values are non-binary strings (character string). They have a character set and values are stored and compared based on the collation of the character set.

    There are four types of TEXT.

    1. TINYTEXT
    2. TEXT
    3. MEDIUMTEXT
    4. LONGTEXT

  • What is the usage of ENUMs in MySQL

  • AENUM is a string object used to specify set of predefined values and that can be used during table creation. Create table size(name ENUM('Small', 'Medium','Large'); 1 Create table size(name ENUM('Small', 'Medium','Large');

  • What are the common MySQL functions

  • ACommon MySQL functions are as follows: • NOWO – function for returning current date and time as single value. • CURRDATEO – function for returning the current date or time. • CONCAT (X, Y) – function to concatenates two string values creating single string output. • DATEDIFF (X, Y) – function to determine difference two dates.

  • Differentiate CHAR_LENGTH and LENGTH

  • ACHAR_LENGTH is character count whereas the LENGTH is byte count. The numbers are same for Latin characters but they are different for Unicode and other encodings.

  • What is the difference between CHAR and VARCHAR

  • A

    A list of differences between CHAR and VARCHAR:

    • CHAR and VARCHAR types are different in storage and retrieval.
    • CHAR column length is fixed to the length that is declared while creating table. The length value ranges from 1 and 255.
    • When CHAR values are stored then they are right padded using spaces to specific length. Trailing spaces are removed when CHAR values are retrieved.

  • Differentiate between FLOAT and DOUBLE? 

  • A

    Following are differences for FLOAT and DOUBLE:

    • Floating point numbers are stored in FLOAT with eight place accuracy and it has four bytes.

    • Floating point numbers are stored in DOUBLE with accuracy of 18 places and it has eight bytes.

  • What are the different tables present in MySQL?

  • A

    There are many tables that remain present by default. But, MyISAM is the default database engine used in MySQL. There are five types of tables that are present:

    • MyISAM
    • Heap
    • Merge
    • INNO DB
    • ISAM

  • What are meant by Joins in MySQL

  • AIn MySQL the Joins are used to query data from two or more tables. The query is made using relationship between certain columns existing in the table. There are four types of Joins in MySQL. Inner Join returns the rows if there is at least one match in both the tables. Left Join returns all the rows form the left table even if there is no match in the right table. Right Join returns all the rows from the right table even if no matches exist in left table. Full Join would return rows when there is at least one match in the tables.

  • What do DDL, DML, and DCL stand for

  • ADDL is the abbreviation for Data Definition Language dealing with database schemas as well as the description of how data resides in the database. An example is CREATE TABLE command. DML denotes Data Manipulation Language such as SELECT, INSERT etc. DCL stands for Data Control Language and includes commands like GRANT, REVOKE etc.

  • What are Heap tables

  • A

    HEAP tables are present in memory and they are used for high speed storage on temporary

    basis.

    • BLOB or TEXT fields are not allowed

    • Only comparison operators can be used =, <,>, = >,=<

    • AUTO_INCREMENT is not supported by HEAP tables

    • Indexes should be NOT NULL

  • What is the difference between database and table

  • AThere is a major difference between a database and a table. The differences are as follows: Tables are a way to represent the division of data in a database while, database is a collection of tables and data. Tables are used to group the data in relation with each other and create a dataset. This dataset will be used in the database. The data which are stored in the table in any form is a part of the database, but the reverse is not true.

  • Why MySQL is used

  • AMySQL database server is reliable, fast and very easy to use. This software can be downloaded as freeware and can be downloaded from the internet.

  • What is the difference between MySQL and SQL

  • ASQL is known as standard query language. It is used to interact with the database like MySQL. MySQL is a database that stores various types of data and keeps it safe. A PHP script is required to store and retrieve the values inside the database.
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