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Articles on Trending Technologies
Technical articles with clear explanations and examples
Set NOT NULL attribute to an existing column in MySQL
To set NOT NULL attribute to an existing column, use ALTER TABLE command. Let us first create a table −mysql> create table DemoTable1949 ( UserId int, UserName varchar(20) ); Query OK, 0 rows affected (0.00 sec)Here is the query to set NOT NULL attribute to an existing column −mysql> alter table DemoTable1949 modify UserName varchar(20) not null; Query OK, 0 rows affected (0.00 sec) Records: 0 Duplicates: 0 Warnings: 0Let us check the description of table −mysql> desc DemoTable1949;This will produce the following output −+----------+-------------+------+-----+---------+-------+ | Field | Type | Null | ...
Read MoreSort only numbers from alphanumeric string in MySQL?
To sort only numbers from alphanumeric string, use ORDER BY RIGHT(). Let us first create a table −mysql> create table DemoTable1948 ( StudentCode varchar(20) ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1948 values('121John_567'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Adam_101'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Bob_563'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Sam_346'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> ...
Read MoreMySQL SELECT from a subquery and then perform DELETE?
Let us first create a table −mysql> create table DemoTable1947 ( Id int, Name varchar(20) ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1947 values(101, 'Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(102, 'David'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(103, 'Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(104, 'Bob'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(105, 'Sam'); Query OK, 1 row affected (0.00 sec)Display ...
Read MoreFetch the count of a specific date in a MySQL table
Let us first create a table −mysql> create table DemoTable1946 ( ShippingDate date ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2018-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2017-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-04-22'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2015-12-11'); Query OK, 1 ...
Read MoreInsert records from multiple tables in MySQL
To insert records from multiple tables, use INSERT INTO SELECT statement. Here, we will insert records from 2 tables.Let us first create a table −mysql> create table DemoTable1943 ( Name varchar(20) ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1943 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1943 values('Robert'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1943;This will produce the following output −+--------+ | Name | +--------+ | Chris ...
Read MoreHow to fetch all databases with name having upper case character after some word using MySQL?
For this, use regular expression. The syntax is as follows −select * from information_schema.schemata WHERE SCHEMA_NAME REGEXP '^yourValue_+[A-Z]';Let us create some databases −mysql> create database bank_APP1; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP2; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP3; Query OK, 1 row affected (0.00 sec)Here is the query to get all databases having upper case character after some word −mysql> select * from information_schema.schemata WHERE SCHEMA_NAME REGEXP '^bank_+[A-Z]';This will produce the following output −+--------------+-------------+----------------------------+------------------------+----------+ | CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH | +--------------+-------------+----------------------------+------------------------+----------+ | def ...
Read MorePython Program to print the diamond shape
The looping features in python can be used to create many nicely formatted diagrams using various characters from the keyboard. One such shape is diamond shape which will involve multiple loops. This is because we have to print the character both vertically and horizontally. Also we have to take care of the shape gradually growing from top till middle and then gradually shrinking from middle till the bottom. For this reason, we will use two for loops each containing one more for loop inside it.Below is the code for creating the diamond shape.Exampledef Shape_of_Diamond(shape): a = 0 for m in ...
Read MoreContingency Table in Python
A contingency table is a table showing the distribution of one variable in rows and another variable in columns. It is used to study the correlation between the two variables. It is a multiway table which describes a dataset in which each observation belongs to one category for each of several variables. Also It is basically a tally of counts between two or more categorical variables. Contingency tables are also called crosstabs or two-way tables, used in statistics to summarize the relationship between several categorical variables.The contingency coefficient is a coefficient of association which tells whether two variables or datasets ...
Read MoreSetting up C++ Development Environment
Text EditorThis will be used to type your program. Examples of few editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi.Name and version of text editor can vary on different operating systems. For example, Notepad will be used on Windows and vim or vi can be used on windows as well as Linux, or UNIX.The files you create with your editor are called source files and for C++ they typically are named with the extension .cpp, .cp, or .c.A text editor should be in place to start your C++ programming.C++ CompilerThis is an actual C++ ...
Read MoreCons of using the whole namespace in C++
In C++, we use different namespaces. We can also create our own namespaces. For example, generally, we use standard namespace called std. We write the syntax like:using namespace std;In the standard library, it contains common functionality you use in building your applications like containers, algorithms, etc. If names used by these were out in the open, for example, if they defined a queue class globally, you'd never be able to use the same name again without conflicts. So they created a namespace, std to contain this change.The using namespace statement just means that in the scope it is present, make ...
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