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Database Articles
Page 284 of 547
What MySQL returns if the search string, provided in FIELD() function, is NULL?
As we know that NULL fails equality comparison with any value hence if the search string, provided in FIELD() function, is NULL then MySQL returns 0 as output.Examplemysql> Select FIELD(NULL,'Ram','is','good','boy'); +-------------------------------------+ | FIELD(NULL,'Ram','is','good','boy') | +-------------------------------------+ | 0 | +-------------------------------------+ 1 row in set (0.00 sec)
Read MoreWhat MySQL returns if the search string is not in the list of strings provided as argument in FIELD() function?
Suppose if the search string is not in the list of strings provided as the arguments in FIELD() function then MySQL will return 0 as output.Examplemysql> Select FIELD('Ram','New','Delhi'); +----------------------------+ | FIELD('Ram','New','Delhi') | +----------------------------+ | 0 | +----------------------------+ 1 row in set (0.00 sec)
Read MoreWhat MySQL returns if we use NULL, as both the arguments, as one of the argument and as a separator, in CONCAT_WS() function?
NULL as both argumentsMySQL returns blank output if we will use NULL as both of the arguments in CONCAT_WS() function.Examplemysql> Select CONCAT_WS('', NULL, NULL); +-------------------------+ | CONCAT_WS('', NULL, NULL) | +-------------------------+ | | +-------------------------+ 1 row in set (0.00 sec)NULL as one of the argumentMySQL returns the value of the other argument as output if we will use NULL as one of the argument in CONCAT_WS() function.Examplemysql> Select CONCAT_WS('', NULL, 'Delhi'); +----------------------------+ | CONCAT_WS('', NULL, 'Delhi') | +----------------------------+ | Delhi ...
Read MoreWhat is the maximum length of data we can put in a TEXT column in MySQL?
As we know TEXT data objects are useful for storing long-form text strings. The different TEXT objects offer a range of storage space from 255 bytes to 4 Gb. The following table shows the storage of different kinds of TEXT data type −Type of BLOBMaximum amount of Data that can be storedOverheadTINYTEXTUp to 255 bytes1 byteTEXTUp to 64 Kb2 bytes MEDIUMTEXTUp to 16 Mb3 bytesLONGTEXTUp to 4 Gb4 bytes
Read MoreWhat 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 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 ...
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