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Articles on Trending Technologies
Technical articles with clear explanations and examples
What are Pure HTML export buttons in jQuery Data Table?
jQuery Data Table provides export buttons with the help of which we can make a structure like the following −Export PDFExport CSVExport HTMLExport ExcelFor this, we need to write code −var tbl = $('#extable').DataTable({ dom: 'export', buttons: [ { extend: 'collection', text: 'Export', buttons: [ 'csvHtml5', ' pdfHtml5', 'copyHtml5', 'excelHtml5' ] } ] });
Read MoreMySQL error 1452 - Cannot add or a child row: a foreign key constraint fails
To understand error 1452, first we need to create a table and relate that to another table with the help of a foreign key constraint.Creating the first table −mysql> CREATE table ForeignTable -> ( -> id int, -> name varchar(200), -> Fk_pk int -> ); Query OK, 0 rows affected (0.43 sec)After creating the first table successfully, we will create the second table −mysql> CREATE table primaryTable1 -> ( -> Fk_pk int, -> DeptName varchar(200), -> Primary key(Fk_pk) -> ); Query OK, 0 rows affected (0.48 sec)Now, we have created both tables. Then both the tables are related with the ...
Read MoreHow to check if a MySQL database exists?
The schema_name command is used to check if a MySQL database exists or not. The syntax of this command is as follows −select schema_name from information_schema.schemata where schema_name = 'database name';Now, the above command is used to check whether the database exists or not. The query for that is as follows −Case 1 − The database exists.mysql> select schema_name from information_schema.schemata where schema_name = 'business'; The output obtained is as follows −+-------------+ | SCHEMA_NAME | +-------------+ | business | +-------------+ 1 row in set (0.00 sec)Case 2 − The database does not exist.mysql> select schema_name from information_schema.schemata ...
Read MoreHow do I see all foreign keys to a table column?
To see all the foreign keys to a table or column, the referenced_column_name command is used.First, two tables are created and then related with the help of the foreign key constraint.Creating the first table −mysql> CREATE table ForeignTable -> ( -> id int, -> name varchar(200), -> Fk_pk int -> ); Query OK, 0 rows affected (0.43 sec)After creating the first table successfully, the second table is created as follows −mysql> CREATE table primaryTable1 -> ( -> Fk_pk int, -> DeptName varchar(200), -> Primary key(Fk_pk) -> ); Query OK, 0 rows affected (0.48 sec)Now, both the tables are related with ...
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 MoreWhat is "where 1=1" statement in MySQL?
In MySQL “Where 1=1” results in all the rows of a table as this statement is always true. An example to better unerstand this statement is given as follows −First, a table is created with the help of the create command. This is given as follows −mysql> CREATE table WhereConditon -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.43 sec)After successfully creating a table, some records are inserted with the help of insert command The query for this is given as follows −mysql> INSERT into WhereConditon values(1, 'John'); Query OK, 1 row affected ...
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 MoreC++ Program to Remove all Characters in a String Except Alphabets
A string is a one-dimensional character array that is terminated by a null character. It may contain characters, digits, special symbols etc.A program to remove all characters in a string except alphabets is given as follows.Example#include using namespace std; int main() { char str[100] = "String@123!!"; int i, j; cout
Read MoreHow to test if a Java String contains a case insensitive regex pattern
the syntax? i:x makes the string search case-insensitive. for egpublic class RegCaseSense { public static void main(String[] args) { String stringSearch = "HI we are at java class."; // this won't work because the pattern is in upper-case System.out.println("Try this 1: " + stringSearch.matches(".*CLASS.*")); // the magic (?i:X) syntax makes this search case-insensitive, so it returns true System.out.println("Try this 2: " + stringSearch.matches("(?i:.*CLASS.*)")); } }
Read MoreHow do I print a double value with full precision using cout in C++?
The output stream cout allows using manipulators that you can use to set the precision directly on cout and use the fixed format specifier. To get the full precision of a double, you can use the limits library. For example,Example#include #include using namespace std; int main() { // Get numeric limits of double typedef std::numeric_limits< double > dbl; double PI = 3.14159265358979; cout.precision(dbl::max_digits10); cout
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