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Articles by Samual Sam
Page 137 of 151
Global memory management in C++ : Stack or Heap?
Stack and heap are used to store variables during the execution of the program and it also get destroyed.Global data structures or global variables are not consumed by stack or heap. They basically allocated in a fixed memory block, which remains unchanged.int a[10]; // located in a fixed memory block int main() { int main() { float *ptr = (int *)malloc(sizeof(float)10.0)); //use heap. } }
Read MoreC++ Program to Implement Hash Tables Chaining with List Heads
A hash table is a data structure which is used to store key-value pairs. Hash function is used by hash table to compute an index into an array in which an element will be inserted or searched.This is a C++ Program to Implement Hash Tables Chaining with List Heads.AlgorithmFor insert:Begin Declare function Insert(int k, int v) int hash_v = HashFunc(k) if (ht[hash_v] == NULL) ht[hash_v] = new ListHead(k, v) else ListHead *en = ht[hash_v] while (en->n != NULL) ...
Read MoreHow to sort time in AM/ PM in MySQL?
To sort time in AM/PM in MySQL, you can use ORDER BY STR_TO_DATE(). Following is the syntax −select yourColumnName from yourTableName ORDER BY STR_TO_DATE(yourColumnName , '%l:%i %p');Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserLogoutTime varchar(200) ); Query OK, 0 rows affected (0.97 sec)Insert records in the table using insert command −mysql> insert into DemoTable(UserLogoutTime) values('09:45 PM'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(UserLogoutTime) values('11:56 AM'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(UserLogoutTime) values('01:01 AM'); Query OK, 1 row affected (0.17 ...
Read MoreHow to know the exact number of table and columns in a MySQL database?
To get the exact number if table and columns in a MySQL database, use the DISTINCT inside COUNT().Let’s say we have a database ‘sample’ and we need to work on it to get the exact number of table and columns.To achieve it, the query is as follows −mysql> SELECT COUNT(DISTINCT TABLE_NAME) AS TotalTable, Count(Column_Name) AS TOTALColumn -> FROM INFORMATION_SCHEMA.COLUMNS -> WHERE TABLE_SCHEMA = 'sample';The following is the output displaying the count of table and columns in the database ‘sample’ −+------------+-------------+ | TotalTable | TOTALColumn | +------------+-------------+ | ...
Read MoreC++ Program to Implement Hash Tables with Double Hashing
A hash table is a data structure which is used to store key-value pairs. Hash function is used by hash table to compute an index into an array in which an element will be inserted or searched.Double hashing is a collision resolving technique in Open Addressed Hash tables. Double hashing uses the idea of using a second hash function to key when a collision occurs.This is a C++ program to Implement Hash Tables chaining with double hashing.AlgorithmFor search a key:Begin Declare Function SearchKey(int k, HashTable *ht) int hashVal= HashFunc1(k, ht->s) int stepSize= HashFunc2(k, ...
Read MoreHow to check if data is NULL in MySQL?
You can use IF() to check if data is NULL. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(200), Age int ); Query OK, 0 rows affected (0.44 sec)Insert records in the table using insert command −mysql> insert into DemoTable(Name, Age) values('John', 23); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(Name, Age) values('Sam', null); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(Name, Age) values('Mike', 23); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(Name, Age) values('David', 21); Query OK, ...
Read MoreC++ Program to Implement Hash Tables with Linear Probing
A hash table is a data structure which is used to store key-value pairs. Hash function is used by hash table to compute an index into an array in which an element will be inserted or searched.Linear probing is a collision resolving technique in Open Addressed Hash tables. In this method, each cell of a hash table stores a single key–value pair. If a collision is occurred by mapping a new key to a cell of the hash table that is already occupied by another key. This method searches the table for the following closest free location and inserts the ...
Read MoreMySQL query to perform delete operation where id is the biggest?
You can use ORDER BY DESC command with LIMIT 1 for this since we need to delete only a single ID.Let us first create a table −mysql> create table DemoTable ( UserId int, UserName varchar(20) ); Query OK, 0 rows affected (0.57 sec)Insert records in the table using insert command −mysql> insert into DemoTable values(100, 'John'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(234, 'Mike'); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable values(145, 'Sam'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(278, 'Carol'); Query OK, 1 ...
Read MoreCan we add a column to a table from another table in MySQL?
Yes, we can add a column to a table from another table. Let us first create two tables. The query to create a table is as follows −mysql> create table FirstTable -> ( -> UserId int, -> UserName varchar(20) -> ); Query OK, 0 rows affected (1.48 sec)Now create the second table. The query to create the second table is as follows −mysql> create table SecondTable -> ( -> UserId int, -> UserAge int -> ); Query OK, 0 rows affected (1.57 sec)Now, add column Age to the first table. Firstly, ...
Read MoreWhich datatype is should I use to set a column for 5-star rating?
You can use ENUM datatype for this. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserRating ENUM('1', '2', '3', '4', '5') ); Query OK, 0 rows affected (0.54 sec)Insert records in the table using insert command −mysql> insert into DemoTable(UserRating) values('5'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable(UserRating) values('3'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(UserRating) values('1'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(UserRating) values('3'); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable(UserRating) values('4'); ...
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