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Articles by Govinda Sai
Page 3 of 5
What's the difference between "STL" and "C++ Standard Library"?
The Standard Template Library (STL) is a software library for the C++ programming language that influenced many parts of the C++ Standard Library. It provides four components called algorithms, containers, functions, and iterators. Note that the term "STL" or "Standard Template Library" does not show up anywhere in the ISO 14882 C++ standard. So referring to the C++ standard library as STL is wrong, ie, STL and C++ Standard Library are 2 different things with the former being the subset of the latter.The STL consists ofContainersThe STL contains sequence containers and associative containers. Containers are objects that store data. The ...
Read MoreWhat is The Rule of Three with reference to C++?
The Rule of three is a rule of thumb when using C++. This is kind of a good practice rule that says that If your class needs any ofa copy constructor, an assignment operator, or a destructor, defined explicitly, then it is likely to need all three of them.Why is this? Its because, if your class requires any of the above, it is managing dynamically allocated resources and would likely be needing the other to successfully achieve that. For example, if you require an assignment operator, you would be creating copies of objects currently being copied by reference, hence allocating ...
Read MoreHow to delete the duplicate values stored in reverse order from MySQL table?
To understand this concept, we are using the data from table ‘Details_city’ as follows −mysql> Select * from details_city; +--------+--------+ | City1 | City2 | +--------+--------+ | Delhi | Nagpur | | Delhi | Mumbai | | Nagpur | Delhi | | Katak | Delhi | | Delhi | Katak | +--------+--------+ 5 rows in set (0.00 sec)Now, the following query will delete the reverse duplicate values from details_city table −mysql> Select a.city1,a.city2 from details_city a WHERE a.city1
Read MoreHow can SELECT, without reference to any table, be used to calculate expression in MySQL?
With the help of following MySQL statement, we can use SELECT to calculate the expression −SELECT expression;The above statement is having no reference to any table. Followings are some examples −mysql> Select 10 DIV 5; +----------+ | 10 DIV 5 | +----------+ | 2 | +----------+ 1 row in set (0.06 sec) mysql> Select 10*5; +------+ | 10*5 | +------+ | 50 | +------+ 1 row in set (0.00 sec) mysql> Set @var1 = 100, @var2 = 200; Query OK, 0 rows affected (0.00 sec) mysql> Select @Var1+@Var2; +-------------+ | @Var1+@Var2 | +-------------+ | 300 | +-------------+ 1 row in set (0.00 sec)
Read MoreHow does MySQL determine the end of the statement?
MySQL determines the end of a statement when it encounters any one of the followings −Semicolon(;)Generally, MySQL determines the end of the statement, single-line or multiple-line, when it encounters the termination semicolon(;). Consider the examples below, mysql> Select * from employee; (Single line statement) mysql> Select * -> from -> employee; (Multiple line statement)In both cases, MySQL returns the result set after encountering the semicolon, which means the end of the statement.\G option\G option means to send the current state to the server to be executed and display the result in a vertical format. When we ...
Read MoreHow can I create a stored procedure to delete values from a MySQL table?
We can create a stored procedure with IN operator to delete values from a MySQL table. To make it understand we are taking an example of a table named ‘student_info’ having the following data −mysql> Select * from student_info; +------+---------+------------+------------+ | id | Name | Address | Subject | +------+---------+------------+------------+ | 100 | Aarav | Delhi | Computers | | 101 | YashPal | Amritsar | History | | 105 | Gaurav ...
Read MoreHow can we find out the storage engine used for a particular table in MySQL?
The following MySQL statement can find out the storage engine used for ‘Student’ table in database named ‘tutorial’ −mysql> SELECT ENGINE FROM information_schema.TABLES -> WHERE TABLE_SCHEMA = 'tutorial' -> AND TABLE_NAME = 'Student'; +--------+ | ENGINE | +--------+ | MyISAM | +--------+ 1 row in set (0.13 sec)
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 | +------------------------------------------+ | ...
Read MoreHow can we remove composite PRIMARY KEY constraint applied on multiple columns of an existing MySQL table?
We can remove composite PRIMARY KEY constraint from multiple columns of an existing table by using DROP keyword along with ALTER TABLE statement.ExampleSuppose we have a table ‘Room_allotment’ having a composite PRIMARY KEY constraint on columns ‘ID’ and ‘RoomNo’ as follows −mysql> describe room_allotment; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | 0 | ...
Read MoreHow to generate prime twins using Python?
Twin primes are pairs of primes which differ by two. The first twin primes are {3,5}, {5,7}, {11,13} and {17,19}. You can generate prime twins in python by running a for loop and checking for primality of the numbers as you do so. exampledef is_prime(n): for i in range(2, n): if n % i == 0: return False return True def generate_twins(start, end): for i in range(start, end): j = i + 2 if(is_prime(i) and is_prime(j)): print("{:d} and {:d}".format(i, j)) generate_twins(2, 100)OutputThis will give the output −3 and 5 5 and 7 11 and 13 17 and 19 29 and 31 41 and 43 59 and 61 71 and 73
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