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 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.
Why MySQL is used?
MySQL 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 are Heap tables?
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 default port for MySQL Server?
The default port for MySQL server is 3306.
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
Give string types available for column?
The string types are:
SET
BLOB
ENUM
CHAR
TEXT
VARCHAR
How to get current MySQL version?
SELECT VERSION ();
1
SELECT VERSION ();
is used to get the current version of MySQL.
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 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.
What are all the Common SQL Function?
CONCAT(A, B) – Concatenates two string values to create a single string output. Often used to combine two or more fields into one single field.
FORMAT(X, D) – Formats the number X to D significant digits.
CURRDATE(), CURRTIME() – Returns the current date or time.
NOW() – Returns the current date and time as one value.
MONTH(), DAY(), YEAR(), WEEK(), WEEKDAY() – Extracts the given data from a date value.
HOUR(), MINUTE(), SECOND() – Extracts the given data from a time value.
DATEDIFF(A, B) – Determines the difference between two dates and it is commonly used to calculate age
SUBTIMES(A, B) – Determines the difference between two times.
FROMDAYS(INT) – Converts an integer number of days into a date value.
Explain Access Control Lists.
An ACL (Access Control List) is a list of permissions that is associated with an object. This list is the basis for MySQL server’s security model and it helps in troubleshooting problems like users not being able to connect.
MySQL keeps the ACLs (also called grant tables) cached in memory. When a user tries to authenticate or run a command, MySQL checks the authentication information and permissions against the ACLs, in a predetermined order.
What are federated tables?
Federated tables which allow access to the tables located on other databases on other servers.
What, if a table has one column defined as TIMESTAMP?
Timestamp field gets the current timestamp whenever the row gets altered.
What happens when the column is set to AUTO INCREMENT and if you reach maximum value in the table?
It stops incrementing. Any further inserts are going to produce an error, since the key has been used already.
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 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.
Why MySQL is used?
MySQL database server is reliable, fast and very easy to use. This software can be downloaded as freeware and can be downloaded from the internet.
 |
| Pegasystems Most Frequently Asked Latest MySQL Interview Questions Answers |
What are Heap tables?
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 default port for MySQL Server?
The default port for MySQL server is 3306.
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
The string types are:
SET
BLOB
ENUM
CHAR
TEXT
VARCHAR
How to get current MySQL version?
SELECT VERSION ();
1
SELECT VERSION ();
is used to get the current version of MySQL.
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 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.
What are all the Common SQL Function?
CONCAT(A, B) – Concatenates two string values to create a single string output. Often used to combine two or more fields into one single field.
FORMAT(X, D) – Formats the number X to D significant digits.
CURRDATE(), CURRTIME() – Returns the current date or time.
NOW() – Returns the current date and time as one value.
MONTH(), DAY(), YEAR(), WEEK(), WEEKDAY() – Extracts the given data from a date value.
HOUR(), MINUTE(), SECOND() – Extracts the given data from a time value.
DATEDIFF(A, B) – Determines the difference between two dates and it is commonly used to calculate age
SUBTIMES(A, B) – Determines the difference between two times.
FROMDAYS(INT) – Converts an integer number of days into a date value.
Explain Access Control Lists.
An ACL (Access Control List) is a list of permissions that is associated with an object. This list is the basis for MySQL server’s security model and it helps in troubleshooting problems like users not being able to connect.
MySQL keeps the ACLs (also called grant tables) cached in memory. When a user tries to authenticate or run a command, MySQL checks the authentication information and permissions against the ACLs, in a predetermined order.
Federated tables which allow access to the tables located on other databases on other servers.
What, if a table has one column defined as TIMESTAMP?
Timestamp field gets the current timestamp whenever the row gets altered.
What happens when the column is set to AUTO INCREMENT and if you reach maximum value in the table?
It stops incrementing. Any further inserts are going to produce an error, since the key has been used already.
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