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Articles on Trending Technologies
Technical articles with clear explanations and examples
How can we specify default values in MySQL INSERT statement?
At the time of creation of a table, if any column is defined with default values then by using the keyword ‘DEFAULT’ in the INSERT statement, we can take default value for that column. For example, we have created a table ‘employee’ with a default value of column ‘DOJ’ as follows −mysql> Create table employee(id int, name varchar(20), doj date DEFAULT '2005-01-01'); Query OK, 0 rows affected (0.09 sec) mysql> Insert into employee(id, name, doj) values(1, ’Aarav’, DEFAULT); Query OK, 1 row affected (0.03 sec) mysql> select * from employee; +------+------------+---------------+ | id | name ...
Read MoreWhat is the proper way to retrieve the value stored in INT column as MySQL TIMESTAMP?
We can use FROM_UNIXTIME() function to retrieve the value, as MySQL TIMESTAMP, stored as INT in the column of a table.For example, we have a table called ‘test123’ which has a column named ‘val1’. In this column, we stored the integer values as follows −mysql> Select * from test123; +------------+ | val1 | +------------+ | 150862 | | 1508622563 | | 622556879 | | 2147483647 | +------------+ 4 rows in set (0.00 sec)Now with the help of the FROM_UNIXTIME() function, we can retrieve the column integer values in the form of MySQL TIMESTAMP data.mysql> Select ...
Read MoreWhy should we not use group functions with non-group fields without GROUP BY clause in MySQL SELECT query?
It is because without GROUP BY clause the output returned by MySQL can mislead. We are giving following example on the ‘Student’ table given below, to demonstrate it −mysql> Select * from Student; +------+---------+---------+-----------+ | Id | Name | Address | Subject | +------+---------+---------+-----------+ | 1 | Gaurav | Delhi | Computers | | 2 | Aarav | Mumbai | History | | 15 | Harshit | Delhi | Commerce | | 20 | Gaurav | Jaipur | Computers | +------+---------+---------+-----------+ 4 rows in set (0.00 sec) mysql> ...
Read MoreHow can we know the repetition of a value in column with the help of group function COUNT(*) and GROUP BY clause?
We can use COUNT(*) and GROUP BY clause to find out the repetition of a value in the column. Following is the example, using COUNT(*) and GROUP BY clause on ‘Name’ column of table ‘Student’, to demonstrate it −mysql> select count(*), name from student group by name; +----------+---------+ | count(*) | name | +----------+---------+ | 1 | Aarav | | 2 | Gaurav | | 1 | Harshit | +----------+---------+ 3 rows in set (0.00 sec)The result set of above query shows that which value is repeated ...
Read More0/1 Knapsack using Branch and Bound in C++
The idea is to implement the fact that the Greedy approach provides the best solution for Fractional Knapsack problem.To check whether a particular node can give us a better solution or not, we calculate the optimal solution (through the node) implementing Greedy approach. If the solution calculated by Greedy approach itself is more than the best so far, then we can’t obtain a better solution through the node.Complete Algorithm is given below −Sort all items according to decreasing order of ratio of value per unit weight so that an upper bound can becalculated implementing Greedy Approach.Initialize maximum profit, such as ...
Read MoreHow can I use 2-digit year value in MySQL DATEDIFF() function?
We can use 2-digit year value either in single date expression or in both date expressions used as argument/s in MySQL DATEDIFF() function.For example, the query below is using 2-digit year value in first date expression and other is having 4-digit year value.mysql> Select DATEDIFF('18-10-22', '2017-10-22'); +-----------------------------------+ | DATEDIFF('18-10-22', '2017-10-22') | +-----------------------------------+ | 365 | +-----------------------------------+ 1 row in set (0.00 sec)And the query below is using 2-digit year value in both date expressions.mysql> Select DATEDIFF('18-10-22', '17-10-22'); +---------------------------------+ | DATEDIFF('18-10-22', '17-10-22') | +---------------------------------+ | ...
Read MoreWhat is the range of date time value that we can pass as an argument to MySQL UNIX_TIMESTAMP function?
The range of date time value that we can pass as an argument to MySQL UNIX_TIMESTAMP function is the same as the range of TIMESTAMP data type i.e. between ‘1970-01-01 00:00:01’ to ‘2038-01-19 08:44:07’. If we give the date time values in UNIX_TIMESTAMP function beyond or below TIMESTAMP range, MySQL will return 0 as output. It can be understood with the help of the following example −mysql> select UNIX_TIMESTAMP('2038-01-19 08:44:07'); +---------------------------------------+ | UNIX_TIMESTAMP('2038-01-19 08:44:07') | +---------------------------------------+ | 2147483647 | +---------------------------------------+ 1 row in set (0.00 sec) ...
Read MoreWhat MySQL returns if I write only one value in the enclosed set of unit values for compound INTERVAL unit?
In this case, MySQL will take into consideration right most unit given in compound INTERVAL unit. It will return the output after calculating the interval on the basis of single value provided in the enclosed set of unit values. The following example will clarify it −mysql> Select TIMESTAMP('2017-10-22 04:05:36' + INTERVAL '2 ' year_month) AS 'Only Month Value Changed'; +--------------------------+ | Only Month Value Changed | +--------------------------+ | 2017-12-22 04:05:36 | +--------------------------+ 1 row in set (0.00 sec)The query above changes the month (right most in compound INTERVAL unit) from 10 to 12 based on the single value ...
Read MoreWhat MySQL returns if I use enclosed set of unit values with INTERVAL keyword?
In this case, MySQL will take into consideration the first value out of two provided in the enclosed set of unit values. It will return the output along with warning after calculating the interval, based on the considered value from an enclosed set, on the unit given in INTERVAL keyword. The following example will clarify it −mysql> Select TIMESTAMP('2017-10-22 04:05:36' + INTERVAL '4 2' Hour)AS 'HOUR VALUE INCREASED BY 4'; +---------------------------+ | HOUR VALUE INCREASED BY 4 | +---------------------------+ | 2017-10-22 08:05:36 | +---------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> Show warnings; +---------+------+------------------------------------------+ | ...
Read MoreHow to sort MySQL output on the basis of the column which is not in the result set?
It is quite possible to get the sorted output on the basis of the column which is not even the part of that output or not in the result set. It can be done by selecting the required fields and writing the name of the fields on the basis of which sorting order is desired. Following is an example to demonstrate it, in which we sorted out the result set, having ‘Name’ and ‘Address’ fields, on the basis of column ‘id’.mysql> Select Name, Subject From Student ORDER BY Id; +---------+-----------+ | Name | Subject | +---------+-----------+ | Gaurav ...
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