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Articles on Trending Technologies
Technical articles with clear explanations and examples
What is the maximum length of data we can put in a BLOB column in MySQL?
As we know that BLOB is a binary large object that can hold a variable amount of data. The different TEXT objects offer a range of storage space from 255 bytes to 4 Gb. Following table shows the storage of different kinds of BLOB data type −Type of BLOBMaximum amount of Data that can be storedOverhead TINYBLOBUp to 255 bytes1 byteBLOBUp to 64 Kb2 bytes MEDIUMBLOBUp to 16 Mb3 bytes LONGBLOBUp to 4 Gb1 Bytes
Read MoreHow wildcard characters can be used with MySQL CONCAT() function?
As we know that wildcards are characters that help search data matching complex criteria. Wildcards are used in conjunction with LIKE comparison operator or NOT LIKE comparison operator. MySQL allows us to match the data, from the output of CONCAT() function, with the help of wildcard and comparison operators LIKE or NOT LIKE. An example from ‘Student’ table is given to make it clearer.Examplemysql> Select CONCAT(Name, ' ', Last_name) AS NAME from student Where CONCAT(Name, ' ', Last_Name) LIKE '%Kumar%'; +---------------+ | NAME | +---------------+ | Gaurav Kumar | | Harshit Kumar | +---------------+ ...
Read MoreWhat MySQL returns if we pass column name, containing a NULL value, as one of the arguments of CONCAT() function?
As we know that CONCAT() function will return NULL if any of the argument of it is NULL. It means MySQL will return NULL if we pass column name, containing a NULL value, as one of the arguments of CONCAT() function. Following is an example of ‘Student’ table to explain it.ExampleIn this example, we are concatenating the values of two strings and at 5th row one, the value is NULL hence the concatenation result is also NULL.mysql> Select Name, Address, CONCAT(Name, ' Resident of ', Address)AS 'Detail of Student' from Student; +---------+---------+---------------------------+ | Name | Address | Detail ...
Read MorePython Regex to extract maximum numeric value from a string
The easiest way to extract the maximum numeric value from a string using regex is to −Use the regex module to extract all the numbers from a stringFind the max from these numbersFor example, for the input string −There are 121005 people in this city, 1587469 in the neighboring city and 18775994 in a far-off city.We should get the output −18775994We can use "\d+" regex to find all numbers in a string as \d signifies a digit and the plus sign finds the longest string of continuous digits. We can implement it using the re package as follows −import re ...
Read MoreWhat happens if I pass only one argument to the MySQL CONCAT() function?
MySQL allows us to pass only one argument to the CONCAT() function. In this case, MySQL returns the same argument as output. Following example will exhibit it −Examplemysql> Select Concat('Delhi'); +-----------------+ | Concat('Delhi') | +-----------------+ | Delhi | +-----------------+ 1 row in set (0.00 sec)
Read MoreUnary or Recursive Relationship
When there is a relationship between two entities of the same type, it is known as a recursive relationship. This means that the relationship is between different instances of the same entity type.Some examples of recursive relationship can be shown as follows −An employee can supervise multiple employees. Hence, this is a recursive relationship of entity employee with itself. This is a 1 to many recursive relationship as one employee supervises many employees.A person can have many children who are also persons. Hence, this is a recursive relationship of entity person with itself. This is a 1 to many recursive ...
Read MoreDDBMS Advantages and Disadvantages
The distributed database management system contains the data in multiple locations. That can be in different systems in the same place or across different geographical locations.As shown in the below example −The database is divided into multiple locations and stores the data in Site1, Site2, Site3 and Site4.The advantages and disadvantages of Distributed database management systems are as follows −Advantages of DDBMSThe database is easier to expand as it is already spread across multiple systems and it is not too complicated to add a system.The distributed database can have the data arranged according to different levels of transparency i.e data ...
Read MoreMobile Databases
Mobile databases are separate from the main database and can easily be transported to various places. Even though they are not connected to the main database, they can still communicate with the database to share and exchange data.The mobile database includes the following components −The main system database that stores all the data and is linked to the mobile database.The mobile database that allows users to view information even while on the move. It shares information with the main database.The device that uses the mobile database to access data. This device can be a mobile phone, laptop etc.A communication link ...
Read MoreMultidimensional Databases
Multidimensional databases are used mostly for OLAP (online analytical processing) and data warehousing. They can be used to show multiple dimensions of data to users .A multidimensional database is created from multiple relational databases. While relational databases allow users to access data in the form of queries, the multidimensional databases allow users to ask analytical questions related to business or market trends.The multidimensional databases uses MOLAP (multidimensional online analytical processing) to access its data. They allow the users to quickly get answers to their requests by generating and analysing the data rather quickly.The data in multidimensional databases is stored in ...
Read MoreHow does MySQL handle overflow during numeric expression assessment?
As we know that MySQL will produce an error if overflow occurs during the assessment of numeric expressions. For example, the largest signed BIGNT is 9223372036854775807, so the following expression will produce an error −mysql> Select 9223372036854775807 + 1; ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807+1)'MySQL can handle such kind of overflows in following ways:BY CONVERTING VALUE TO UNSIGNEDMySQL enables such kind of operations by converting the values to unsigned as follows −mysql> Select CAST(9223372036854775807 AS UNSIGNED) +1; +------------------------------------------+ | CAST(9223372036854775807 AS UNSIGNED) +1 | +------------------------------------------+ | ...
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