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Articles on Trending Technologies
Technical articles with clear explanations and examples
How can I insert a value in a column at the place of NULL using MySQL COALESCE() function?
To understand it, we are using the data from the table ‘Employee’ having Salary=NULL for ID = 5 and 6, as follows −mysql> Select * from Employee; +----+--------+--------+ | ID | Name | Salary | +----+--------+--------+ | 1 | Gaurav | 50000 | | 2 | Rahul | 20000 | | 3 | Advik | 25000 | | 4 | Aarav | 65000 | | 5 | Ram | NULL | | 6 | Mohan | NULL | +----+--------+--------+ 6 rows in set (0.00 sec)Now, the following queries will use COALESCE() function along with UPDATE and ...
Read MoreWhat is the difference between a class and an object in C#?
When you define a class, you define a blueprint for a data type.Objects are instances of a class. The methods and variables that constitute a class are called members of the class.To access the class members, you use the dot (.) operator after the object name. The dot operator links the name of an object with the name of a member for example, Box Box1 = new Box();Above you can see Box1 is our object. We will use it to access the members −Box1.height = 7.0;You can also use it to call member functions −Box1.getVolume();The following is an example showing ...
Read MoreHow can I check the list of MySQL tables, in the current database we are using, along with table type in the result set?
It can be done with the SHOW FULL TABLES statement. Its Syntax would be as follows −SyntaxSHOW FULL TABLESExampleIn the following example our current database is ‘query’ hence the statement below will show us the table list along with table type in the result set from this database −mysql> SHOW FULL TABLES; +-----------------------------+------------+ | Tables_in_query | Table_type | +-----------------------------+------------+ | accounts | BASE TABLE | | address | BASE TABLE | | cars ...
Read MoreWhat are the differences between constructors and destructors in C#?
ConstructorsA class constructor is a special member function of a class that is executed whenever we create new objects of that class.A constructor has exactly the same name as that of class and it does not have any return type.Constructor has the same name as the class name −class Demo { public Demo() {} }The following is an example −Example Live Demousing System; namespace LineApplication { class Line { private double length; // Length of a line public Line() { Console.WriteLine("Object is being created"); ...
Read MoreWhich MySQL query can be used with the help of which we can see the list of MySQL databases?
With the help of following MySQL query, we can see the list of MySQL database −mysql> SELECT schema_name FROM information_schema.schemata; +--------------------+ | schema_name | +--------------------+ | information_schema | | gaurav | | mysql | | performance_schema | | query | | query1 | | sys | | tutorials | +--------------------+ 8 rows in set (0.00 sec)We can also use WHERE clause with this query as follows −mysql> SELECT schema_name FROM information_schema.schemata WHERE schema_name LIKE '%schema' OR schema_name LIKE '%s'; +--------------------+ | schema_name | +--------------------+ | information_schema | | performance_schema | | sys | | tutorials | +--------------------+ 4 rows in set (0.00 sec)
Read MoreWhat is the use of CHECK TABLE statement in maintaining the MySQL tables?
There may be something wrong which can happen to the database server e.g., the server was shutdown unexpectedly, error while writing data to the hard disk, etc. These situations could make the database operate incorrectly and in the worst case, it can be crashed.With the help of CHECK TABLE statement MySQL allows us to check the integrity of database tables. Its syntax would be as follows −CHECK TABLE table_nameHere, table_name is the name of the table.ExampleWe are running this statement for the table Student_info as follows −mysql> CHECK table student_info\G *************************** 1. row *************************** Table: query.student_info ...
Read MoreWhat are the differences between ref and out parameters in C#?
Ref ParameterA reference parameter is a reference to a memory location of a variable. When you pass parameters by reference, unlike value parameters, a new storage location is not created for these parameters.You can declare the reference parameters using the ref keyword. The following is an example −Example Live Demousing System; namespace CalculatorApplication { class NumberManipulator { public void swap(ref int x, ref int y) { int temp; temp = x; /* save the value of x */ x = y; /* put ...
Read MoreWhat are the differences between class methods and class members in C#?
A member function i.e. method of a class is a function that has its definition or its prototype within the class definition similar to any other variable. It operates on any object of the class of which it is a member, and has access to all the members of a class for that object.The following is an example −public void setLength( double len ) { length = len; } public void setBreadth( double bre ) { breadth = bre; }The following is an example showing how to access class member functions in C# −Example Live Demousing System; ...
Read MoreWhat does the @ prefix do on string literals in C#?
The @prefix states hat you don't need to escape special characters in the string following to the symbol.The following statement@"D:ew"is equal to:"D:ew"The @ prefix is also used if you want to have large strings and want it to be displayed across multiple lines. The following is an example showing multi-line string −Example Live Demousing System; namespace Demo { class Program { static void Main(string[] args) { string str = @"Welcome User, Kindly wait for the image to load"; Console.WriteLine(str); } } }OutputWelcome User, Kindly wait for the image to load
Read MoreWhich MySQL function is used to find first non-NULL value from a list of values?
We can use MySQL COALESCE() function to get the first non-NULL value as output from a list of values. In other words, this function will check all the values until non-null value found. It can take one or more than one argument. It is having the following syntax:COALESCE(value1, value2, …, valueN)ExampleFollowing is an example to demonstrate it −mysql> Select COALESCE(NULL, NULL, NULL, 'Ram', 'Aarav', NULL); +--------------------------------------------------+ | COALESCE(NULL, NULL, NULL, 'Ram', 'Aarav', NULL) | +--------------------------------------------------+ | Ram | +--------------------------------------------------+ 1 row in set (0.00 sec)
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