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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to identify composite primary key in any MySQL database table?
You can use aggregate function count(*). If it returns a value greater than 1, that would mean the table has composite primary key.Let us first create a table −mysql> create table DemoTable1324 -> ( -> StudentId int, -> StudentName varchar(20), -> StudentAge int, -> StudentCountryName varchar(20) -> ); Query OK, 0 rows affected (0.52 sec)Here is the query to add composite primary key −mysql> alter table DemoTable1324 ADD CONSTRAINT constr_IdAgeCountry PRIMARY KEY (StudentId, StudentAge, StudentCountryName); Query OK, 0 rows affected (1.29 sec) Records: 0 Duplicates: 0 Warnings: 0Following is the query to identify composite ...
Read MoreMySQL query to get the last created table name (most recent)?
You can use the concept INFORMATION_SCHEMA.TABLES for this. Let us first create a table. This would be our most recent table −mysql> create table DemoTable1323 -> ( -> FirstName varchar(10) -> ); Query OK, 0 rows affected (0.43 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1323 values('Chris'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1323 values('David'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1323 values('Bob'); Query OK, 1 row affected (0.11 sec)Display all records from the table using select statement −mysql> select *from DemoTable1323;This will produce ...
Read MoreCreate a MySQL table from already created table selecting specific rows?
To create a table from an already created table, use CREATE TABLE AS SELECT statement. Let us first create a table −mysql> create table DemoTable1318 -> ( -> Id int, -> FirstName varchar(10), -> LastName varchar(10), -> Age int -> ); Query OK, 0 rows affected (0.50 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1318 values(1, 'Chris', 'Brown', 21); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable1318 values(2, 'David', 'Miller', 24); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1318 values(3, 'Carol', 'Taylor', 23); Query OK, 1 row affected (0.11 ...
Read MoreHow do I return multiple results in a MySQL subquery with IN()?
In MySQL, you can easily return multiple results, but also achieve this with subquery using IN(). Let us first create a table −mysql> create table DemoTable1317 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.49 sec)Insert some records in the table using insert commandmysql> insert into DemoTable1317(Name) values('Chris Brown'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1317(Name) values('John Doe'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1317(Name) values('Adam Smith'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1317(Name) values('John Smith'); ...
Read MoreSelect words from a text already in a MySQL table
Let us first create a table −mysql> create table DemoTable1316 -> ( -> Value varchar(40) -> ); Query OK, 0 rows affected (0.47 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1316 values('MySQL'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1316 values('Java'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1316 values('MongoDB'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable1316 values('C++'); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select *from DemoTable1316;This will produce the following output. These are the ...
Read MoreMySQL query to convert empty values to NULL?
It’s easy to convert empty values to NULL using SET and WHERE. Let us first create a table −mysql> create table DemoTable1315 -> ( -> CountryName varchar(10) -> ); Query OK, 0 rows affected (0.60 sec)Insert some records in the table using insert command. We have set some empty values here as well −mysql> insert into DemoTable1315 values('US'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1315 values(''); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable1315 values('UK'); Query OK, 1 row affected (0.70 sec) mysql> insert into DemoTable1315 values(''); Query OK, 1 row affected (0.12 ...
Read MoreMySQL query to display records ordered by numeric difference?
Use ORDER BY and set the difference to display records ordered by numeric difference. Following is the syntax −select *from yourTableName order by (yourIntegerColumnName1 - yourIntegerColumnName2);Let us first create a table −mysql> create table DemoTable1313 -> ( -> Name varchar(20), -> Score1 int, -> Score2 int -> ); Query OK, 0 rows affected (3.48 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1313 values('Chris', 40, 60); Query OK, 1 row affected (0.38 sec) mysql> insert into DemoTable1313 values('David', 70, 50); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1313 values('Adam', 35, 30); Query OK, ...
Read MoreHow to use a comma-separated string in an `IN ()` in MySQL?
Set the comma-separated string in the IN() as in the below syntax:select *from yourTableName where yourColumnName IN('yourCommaSeparatedValue');Let us first create a table −mysql> create table DemoTable1314 -> ( -> Number varchar(100) -> ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1314 values('45, 67, 89'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1314 values('10, 20, 50'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1314 values('90, 56, 45'); Query OK, 1 row affected (0.23 sec)Display all records from the table using select statement −mysql> select ...
Read MoreA single query to get the sum of count from different tables in MySQL?
To get the sum of count from different tables, use UNION ALL. Let us first create a table −mysql> create table DemoTable1 -> ( -> Id int, -> Name varchar(30) -> ); Query OK, 0 rows affected (1.55 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values(10, 'Chris Brown'); Query OK, 1 row affected (0.83 sec) mysql> insert into DemoTable1 values(20, 'David Miller'); Query OK, 1 row affected (0.50 sec) mysql> insert into DemoTable1 values(30, 'John Adam'); Query OK, 1 row affected (0.83 sec)Display all records from the table using select statement −mysql> select *from ...
Read MoreFind the smallest number X such that X! contains at least Y trailing zeros in C++
We have to take a number Y, we will find smallest number X, such that X! contains at least Y number of training zeros. For example, if Y = 2, then the value of X = 10. As X! = 3228800. It has Y number of zeros.We can solve this using binary search. The number of trailing zeros in N! is given by the count of the factors 5 in N!. X can be found using binary search in range [0, 5*Y]Example #include using namespace std; int factorCount(int n, int X) { if (X < n) ...
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