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Articles on Trending Technologies
Technical articles with clear explanations and examples
C++ program to find cabs nearby using Great Circle Distance formula
In this article, we will be discussing a program to find the cabs near about (less than 50km) using the Great Circle Distance formula.Let us suppose we have been given a JSON file which contains the name and coordinates of the people who need a cab and also the coordinates of the all the cabs available.To solve this, we would convert the GPS coordinates into double. From the double form, we would finally convert them in degrees to radians. Then we can ultimately apply the Great Circle Distance formula to find the cabs available in 50km from the user’s position.Note ...
Read MoreMySQL query to get count of each fileid entry in a table with Id and FileIDs?
Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FileID int ) AUTO_INCREMENT=100; Query OK, 0 rows affected (1.36 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(FileID) values(50); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(FileID) values(60); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(FileID) values(50); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(FileID) values(70); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable(FileID) values(60); Query OK, 1 row affected (0.28 sec) mysql> ...
Read MoreCreate a table if it does not already exist and insert a record in the same query with MySQL
Use CREATE TABLE IF NOT EXISTS for this as shown in the below syntax −create table if not exists yourTableName ( yourColumnName1 dataType, yourColumnName2 dataType, yourColumnName3 dataType, . . N ) as select yourValue1 as yourColumnName1 , yourValue2 as yourColumnName2 , yourValue3 as yourColumnName3, .............................N;Let us first create a table and insert value if the table does not already exist −mysql> create table if not exists DemoTable ( id int, FirstName varchar(20), LastName varchar(20) ) as select 100 as id, 'John' as FirstName , 'Smith' as LastName; Query OK, 1 row ...
Read MoreHow to display a single quote text as a column value in MySQL?
To display a single quote text, use double quotes like if you want to write You’ve, then write You've while inserting i.e. with double-quotes. Let us first create a table −mysql> create table DemoTable ( Note text ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('You''ve seen the Taj? When?'); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values('You''ve visited the US?'); Query OK, 1 row affected (0.16 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the ...
Read MoreUpdating blank cells to NULL will cause all cells to be NULL in MySQL?
To update only blank cells to NULL, use NULLIF() in MySQL. Let us first create a table −mysql> create table DemoTable ( Name varchar(50) ); Query OK, 0 rows affected (1.73 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable values(''); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable values(''); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.15 ...
Read MoreHow to implement MAX(distinct...) in MySQL and what is the difference without using DISTINCT?
Let us see the first syntax, which uses DISTINCT in MAX() −select max(DISTINCT yourColumnName) from yourTableName;The second syntax is as follows. It isn’t using DISTINCT −select max( yourColumnName) from yourTableName;NOTE − Both the above queries give the same result with or without a DISTINCT keyword. MySQL internally converts MAX(yourColumnName) to DISTINCT keyword.Let us now see an example and create a table −mysql> create table DemoTable ( Number int ); Query OK, 0 rows affected (1.50 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(80); Query OK, 1 row affected (0.09 sec) mysql> insert into ...
Read MoreIn MySQL stored procedures, how to check if a local variable is null?
For this, use COALESCE(). Let us implement a stored procedure to check if the local variable is null −mysql> DELIMITER // mysql> CREATE PROCEDURE local_VariableDemo() BEGIN DECLARE value1 int; DECLARE value2 int; select value1, value2; select concat('After checking local variable is null the sum is = ', COALESCE(value1, 0)+COALESCE(value2, 0)); END // Query OK, 0 rows affected (0.19 sec) mysql> DELIMITER ;Call the stored procedure using CALL command −mysql> call local_VariableDemo();This will produce the following output −+--------+--------+ | value1 | value2 | +--------+--------+ | NULL | NULL | +--------+--------+ 1 ...
Read MoreSET only two values for all the rows in a MySQL table based on conditions?
For condition based update, use UPDATE and IF(). Let us first create a table −mysql> create table DemoTable ( Value int ); Query OK, 0 rows affected (0.47 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable values(20); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(20); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(30); Query OK, 1 row affected (0.10 sec)Display all records ...
Read MoreHow can I match a comma separated list against a value in MySQL?
Let us first create a table −mysql> create table DemoTable ( `Values` varchar(50) ); Query OK, 0 rows affected (1.15 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('23, 45, 78, 56'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('384, 476, 7456'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('68, 8, 88, 89'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values('78, 80, 84'); Query OK, 1 row affected (0.19 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This ...
Read MoreMySQL query to fetch only a single field on the basis of boolean value in another field
Let us first create a table −mysql> create table DemoTable ( EmployeeId int NOT NULL AUTO_INCREMENT PRIMARY KEY, EmployeeName varchar(40), isMarried boolean ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(EmployeeName, isMarried) values('Chris', true); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(EmployeeName, isMarried) values('Robert', false); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable(EmployeeName, isMarried) values('Mike', false); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable(EmployeeName, isMarried) values('Bob', true); Query OK, 1 row affected (0.07 sec) mysql> insert into ...
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