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The Stack is Last In First Out (LIFO) data structure. This data structure has some important applications in different aspect. These are like below −Expression Handling −Infix to Postfix or Infix to Prefix Conversion −The stack can be used to convert some infix expression into its postfix equivalent, or prefix equivalent. These postfix or prefix notations are used in computers to express some expressions. These expressions are not so much familiar to the infix expression, but they have some great advantages also. We do not need to maintain operator ordering, and parenthesis.Postfix or Prefix Evaluation −After converting into prefix or ... Read More
Regular functions vs Arrow functionsAn arrow function is used to write the code concisely. Both functions regular and arrow work in a similar manner but there are some differences between them. Let's discuss those differences in a nutshell.syntax of an arrow functionlet x = (params) => { // code };syntax of a regular functionlet x = function functionname(params){ // code };Usage of "this" keywordIt is unable to use "this" keyword in arrow functions whereas in regular functions it can be used without any disturbance.ExampleIn the following example, both regular(rectangle) and arrow(square) functions were used inside the object "num", which consists of len(length) ... Read More
The recursion is a process by which a function calls itself. We use recursion to solve bigger problem into smaller sub-problems. One thing we have to keep in mind, that if each sub-problem is following same kind of patterns, then only we can use the recursive approach.A recursive function has two different parts. The base case and the recursive case. The base case is used to terminate the task of recurring. If base case is not defined, then the function will recur infinite number of times (Theoretically).In computer program, when we call one function, the value of the program counter ... Read More
We can able to access the existing object by creating its own prototype using a javascript method called "Object.create()". Using this method we can inherit the properties from the existing properties to the newly created prototype. Let's discuss it in a nutshell.syntaxObject.create(existing obj);This method takes the existing object and creates its own prototype so that the properties will be inherited from the existing object to the newly created prototype.ExampleIn the following example, Initially, an object named "person" is created and the using "Object.create" its own prototype is created and assigned to a variable "newper". Later on, using the prototype the ... Read More
To check for NULL, use the IS NULL. For empty values, you need to check with an empty string. We will now see an example.Let us first create a table −mysql> create table DemoTable691( PlayerId int NOT NULL AUTO_INCREMENT PRIMARY KEY, PlayerName varchar(100), PlayerScore int ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable691(PlayerName, PlayerScore) values('Robert', 56); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable691(PlayerName, PlayerScore) values('David', 89); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable691(PlayerName, PlayerScore) values('', 98); Query ... Read More
Let us first see a case wherein we use “create table table” while creating a table. An error will arise −mysql> create table table( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(100) );This will produce the following output i.e. error −ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(100) )' at line 1As you can see above, the word “table” is a reserved keyword, and we ... Read More
To select records that begin with a specific value, you need to use LIKE operator. Let us first create a table −mysql> create table DemoTable690( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserValue varchar(100) ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable690(UserValue) values('567890'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable690(UserValue) values('789032'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable690(UserValue) values('567342'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable690(UserValue) values('890678'); Query OK, 1 row affected (0.16 sec)Display ... Read More
This kind of errors arise when you have used incorrect syntax. Let us see an example wherein we have created a table and the same error “1054” arise.Here’s the table −mysql> create table DemoTable689( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserName varchar(100), UserLoginDate date(100) NOT NULL );This will produce the following output i.e. an error for incorrect syntax usage −ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(100) NOT NULL )' at line 5Let us now ... Read More
To find missing value between two MySQL tables, use NOT IN. Let us first create a table −mysql> create table DemoTable1(Value int); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values(1); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1 values(2); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable1 values(5); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable1 values(6); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable1 values(8); Query OK, 1 row affected (0.16 sec)Display all records from ... Read More
Let us first create a table −mysql> create table DemoTable1(Name varchar(100)); Query OK, 0 rows affected (0.83 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values('John'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable1 values('Chris'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1 values('Robert'); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select *from DemoTable1;This will produce the following output −+--------+ | Name | +--------+ | John | | Chris | | Robert | +--------+ 3 ... Read More