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Articles by George John
Page 47 of 79
What is the MySQL VARCHAR max size?
The MySQL version before 5.0.3 was capable of storing 255 characters but from the version 5.0.3 , it is capable of storing 65, 535 characters.MySQL official documentation states −The effective maximum length of a VARCHAR in MySQL 5.0.3 and later is subject to the maximum row size (65, 535 bytes, which is shared among all columns) and the character set used. For example, utf8 characters can require up to three bytes per character, so a VARCHAR column that uses the utf8 character set can be declared to be a maximum of 21, 844 characters. Keep in mind that the limitation of ...
Read MoreDifference between Schema and Database in MySQL?
In MySQL, schema is synonymous with database. As the query is written to create the database, similarly the query can be written to create the schema.Logical structure can be used by the schema to store data while memory component can be used by the database to store data. Also, a schema is collection of tables while a database is a collection of schema.To clarify this concept, a database and a schema are created. The steps for this are as follows −First, a database is created with the following syntax −create database yourDatabaseName;The above syntax is used in a query as ...
Read MoreHow to change max_allowed_packet size in MySQL?
The max_allowed_packet size is a session variable and is also a read only variable.To check what is the present value of max_allowed_packet, the command show variables is used. It is given as follows −mysql> show variables like 'max_allowed_packet';The following is the output+--------------------+---------+ | Variable_name | Value | +--------------------+---------+ | max_allowed_packet | 4194304 | +--------------------+---------+ 1 row in set (0.04 sec)The value of the max_allowed_packet can be changed in the ‘my.ini’ file on the client side. The query for that is given as follows −max_allowed_packet = 4567890; Now, the value can be changed globally ...
Read MoreHow to modify the size of column in MySQL table?
We can modify a column size with the help of ALTER command. Let us see how to modify column size. Suppose we are defining any column with some size. At the time of inserting if we are giving more size in comparison to the one we defined, then an error will generate.The above problem can be reduced while modifying the size. For more understanding, we can create a table with the help of CREATE command −mysql> CREATE table ModifyColumnNameDemo -> ( -> id int, -> StudentName varchar(10) -> ); Query OK, 0 rows affected (0.45 sec)After creating a table successfully, ...
Read MoreRegular cast vs. static_cast vs. dynamic_cast in C++
static_cast − This is used for the normal/ordinary type conversion. This is also the cast responsible for implicit type coersion and can also be called explicitly. You should use it in cases like converting float to int, char to int, etc.dynamic_cast −This cast is used for handling polymorphism. You only need to use it when you're casting to a derived class. This is exclusively to be used in inheritence when you cast from base class to derived class.Regular Cast − This is the most powerful cast available in C++ as it combines const_cast, static_cast and reinterpret_cast. but it's also unsafe ...
Read MoreRule of Three vs Rule of Five in 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 MoreWhat are the differences between -std = c++11 and -std = gnu++11?
GNU C++ compiler, g++, provides extensions to the C++ language. The difference between the two options is whether these GNU extensions that might violate the C++ standard are enabled or not. Note that some extensions can still be in effect when using -std = c++11, if they don't violate the standard.The list of extensions to the C++ language in GNU compiler can be found here − https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Extensions.html
Read MoreC++11 Overview
C++11 is the modern C++ standard published in 2011. This brought many major extensions and improvements to the existing language. It was approved by International Organization for Standardization (ISO) on 12 August 2011 and replaced C++03.C++11 was also known as C++0x. This is because, For the next revision, it was supposed that the next Standard after would be done by 2008, but since it was uncertain, it was named C++0x, where the x stood for either 8 or 9. Though planning shifted and it is now called C++11. So, C++0x was the name for the standard before it was published. ...
Read MoreHow to access a local variable from a different function using C++ pointers?
You can't access a local variable once it goes out of scope. This is what it means to be a local variable. Though, Let us look at an example where you MIGHT be able to access a local variable's memory outside its scope.Example#include int* foo() { int x = 3; return &x; } int main() { int* address = foo(); cout
Read MoreHow can we create a MySQL view based on another existing view?
In MySQL, we can create a view that is based on another existing view. To make it understand we are having the view ‘Info’ with the following data −mysql> Create view info AS Select Id, Name, Subject FROM student_info; Query OK, 0 rows affected (0.11 sec) mysql> Select * from Info; +------+---------+------------+ | Id | Name | Subject | +------+---------+------------+ | 101 | YashPal | History | | 105 | Gaurav | Literature | | 125 | Raman | Computers | | NULL | Ram | Computers | +------+---------+------------+ 4 rows in set (0.00 sec)Now, with the help of ...
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