What is MySQL?
MySQL is a multithreaded, multi-user SQL database management system which has more than 11 million installations. This is the world's second most popular and widely used open source database.
What are the technical features of MySQL?
MySQL database software is a client or server system which includes
  • Multithreaded SQL server supporting various client programs and libraries
  • Different backend
  • Wide range of application programming interfaces and
  • Administrative tools
What are the technical specification of MySQL?
MySQL has the following technical specifications -
  • Flexible structure
  • High performance
  • Manageable and easy to use
  • Replication and high availability
  • Security and storage management
What are the advantages of MySQL when compared with Oracle?
  • MySQL is open source software which is available at any time and has no cost involved.
  • MySQL is portable
  • GUI with command prompt.
  • Administration is supported using MySQL Query Browser
What are the disadvantages of MySQL?
  • MySQL is not so efficient for large scale databases.
  • It does not support COMMIT and STORED PROCEDURES functions version less than 5.0.
  • Transactions are not handled very efficiently.
How many Triggers are possible in MySQL?
There are only six Triggers allowed to use in MySQL database.
  1. Before Insert
  2. After Insert
  3. Before Update
  4. After Update
  5. Before Delete
  6. After Delete
Differentiate between 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.
Differentiate CHAR_LENGTH and LENGTH?
CHAR_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 BLOB and TEXT in MySQL?
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 difference between MySQL_connect and MySQL_pconnect?
MySQL connect:
  • It opens a new connection to the database.
  • Every time you need to open and close database connection, depending on the request.
  • Opens page every time when it loaded.
MySQL_pconnect:
  • In MySQL_pconnect, "p" stands for persistent connection so it opens the persistent connection.
  • the database connection cannot be closed.
  • it is more useful if your site has more traffic because there is no need to open and close connection frequently and every time when page is loaded.
What are the security alerts while using MySQL?
  • Install antivirus and configure the operating system's firewall.
  • Never use the MySQL Server as the UNIX root user.
  • Change root username and password.
  • Restrict or disable remote access.
Difference between CHAR and VARCHAR?
Following are the differences between CHAR and VARCHAR:
  • CHAR and VARCHAR types differ 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.
What storage engines are used in MySQL?
Storage engines are called table types and data is stored in files using various techniques.
Technique involves:
  • Storage mechanism
  • Locking levels
  • Indexing
  • Capabilities and functions
What are the drivers in MySQL?
  • PHP Driver
  • JDBC Driver
  • ODBC Driver
  • C WRAPPER
  • PYTHON Driver
  • PERL Driver
  • RUBY Driver
  • CAP11PHP Driver
  • Ado.net5.mxj
What is the difference between primary key and candidate key?
Every row of a table is identified uniquely by primary key. There is only one primary key for a table.
Primary Key is also a candidate key. By common convention, candidate key can be designated as primary and which can be used for any foreign key references.
How do you login to MySQL using Unix shell?
We can login through this command:
# [mysql dir]/bin/mysql -h hostname -u <UserName> -p <password>
What is the difference between MyISAM Static and MyISAM Dynamic?
In MyISAM static all the fields will have fixed width. The Dynamic MyISAM table will have fields like TEXT, BLOB, etc. to accommodate the data types with various lengths.
MyISAM Static would be easier to restore in case of corruption.
Where MyISAM table will be stored and also give their formats of storage?
Each MyISAM table is stored on disk in three formats:
  • The ‘.frm’ file stores the table definition
  • The data file has a ‘.MYD’ (MYData) extension
  • The index file has a ‘.MYI’ (MYIndex) extension
What is the difference between mysql_fetch_array and mysql_fetch_object?
Following are the differences between mysql_fetch_array and mysql_fetch_object:
  • mysql_fetch_array() -Returns a result row as an associated array or a regular array from database.
  • mysql_fetch_object – Returns a result row as object from database.
What are the different tables present in MySQL?
Total 5 types of tables are present:
  1. MyISAM
  2. Heap
  3. Merge
  4. INNO DB
  5. ISAM
What are the objects can be created using CREATE statement?
Following objects are created using CREATE statement:
  • DATABASE
  • EVENT
  • FUNCTION
  • INDEX
  • PROCEDURE
  • TABLE
  • TRIGGER
  • USER
  • VIEW
What is save point in MySQL?
A defined point in any transaction is known as savepoint.
SAVEPOINT is a statement in MySQL which is used to set a named transaction save point with a name of identifier.
What is SQLyog?
SQLyog program is the most popular GUI tool for admin. It is the most popular MySQL manager and admin tool. It combines the features of MySQL administrator, phpMyadmin and others MySQL front ends and MySQL GUI tools.
How do you backup a database in MySQL?
It is easy to backing up data with phpMyadmin. Select the database you want to backup by clicking the database name in the left hand navigation bar. Then click the export button and make sure that all tables are highlighted that you want to backup. Then specify the option you want under export and save the output.
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