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Articles by Arjun Thakur
Page 47 of 75
How can we convert subqueries to RIGHT JOIN?
To make it understand we are using the data from the following tables −mysql> Select * from Customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | Rahul | | 2 | Yashpal | | 3 | Gaurav | | 4 | Virender | +-------------+----------+ 4 rows in set (0.00 sec) mysql> Select * from Reserve; +------+------------+ | ID | Day | +------+------------+ | 1 | 2017-12-30 | | ...
Read MoreHow can we use a MySQL subquery with INSERT statement?
It can be understood with the help of an example in which we would copy the values of a table into other table. We are using the data from table ‘cars’ and copy its data to table ‘copy_cars’ −mysql> CREATE TABLE copy_cars LIKE cars; Query OK, 0 rows affected (0.86 sec) mysql> SELECT * from copy_cars; Empty set (0.08 sec)The following query using the subquery will insert the values same as ‘cars’ to table ‘copy_cars’ −mysql> INSERT INTO Copy_cars Select * from Cars; Query OK, 8 rows affected (0.07 sec) mysql> SELECT * from copy_cars; +------+--------------+---------+ | ID ...
Read MoreHow can we retrieve the output having decimal values of a column in a specified format?
MySQL FORMAT() function, converts a number to a format like #, ###, ###.### which is rounded up to the number of decimal places specified and returns the result as a string, can be used to retrieve the output having decimal values of a column in a specified format. To understand it, we are taking an example of table ‘estimated_cost’ which have the following data −mysql> Select * from estimated_cost; +----+-----------------+-----------+---------------+ | Id | Name_Company | Tender_id | Tender_value | +----+-----------------+-----------+---------------+ | 1 | ABC Ltd. | 110 ...
Read MoreWhen MySQL IN() function returns NULL?
Following are the two cases when MySQL IN() function returns NULL as result −Case-1 − When expression on left side is NULL IN() function will return NULL if the expression on the left side is NULL. Following example will demonstrate it −mysql> Select NULL IN (1, 2, 3, 4, 10); +----------------------+ | NULL IN (1, 2, 3, 4, 10) | +----------------------+ | NULL | +----------------------+ 1 row in set (0.00 sec)Case-2 − When one of expression in the list is NULL and no ...
Read MoreWhat is the use of IGNORE_SPACE SQL mode?
The IGNORE_SPACE SQL mode can be used to modify how the parser treats function names that are whitespace-sensitive. Following are the cases in which we can use IGNORE_SPACE SQL mode −Case-1 − When IGNORE_SPACE SQL mode is disabledAfter disabling the IGNORE_SPACE SQL mode, the parser interprets the name as a function call when there is no whitespace between the name and the following parenthesis. This also occurs when the function name is used in a non-expression context. It can be understood from the following query −mysql> Create table SUM(Id Int); ERROR 1064 (42000): You have an error in your ...
Read MoreHow can I customize the output of MySQL SUM() function to 0 instead of NULL when there are no matching rows?
As we know that the SUM() function returns NULL if there is no matching row but sometimes we want it to return zero instead of NULL. For this purpose, we can use the MySQL COALESCE() function which accepts two arguments and returns the second argument if the first argument is NULL, otherwise, it returns the first argument. To understand the above concept, consider an ‘employee_tbl’ table, which is having the following records −mysql> SELECT * FROM employee_tbl; +------+------+------------+--------------------+ | id | name | work_date | daily_typing_pages | +------+------+------------+--------------------+ | 1 | John | 2007-01-24 ...
Read MoreHow can we update MySQL table after removing a particular string from the values of column?
We can update MySQL table after removing a particular string from the values of a column by using TRIM() function along with UPDATE clause. Following the example from ‘examination_btech’ table will make it clearer −ExampleSuppose if we want to delete the values ‘(CSE)’, from last, of column ‘Course’ and want to update the table too then it can be done with the help of the following query −mysql> Update examination_btech SET Course = TRIM(Trailing '(CSE)' FROM Course); Query OK, 10 rows affected (0.13 sec) mysql> Select * from examination_btech; +-----------+----------+--------+ | RollNo | Name ...
Read MoreHow MySQL evaluates an empty hexadecimal value?
Actually, MySQL evaluates an empty hexadecimal value to a zero-length binary string. It can be demonstrated as follows −mysql> Select CHARSET(X''); +--------------+ | CHARSET(X'') | +--------------+ | binary | +--------------+ 1 row in set (0.00 sec)The above result set shows that the empty hexadecimal value is a binary string. And the result set below shows that it is of length 0.mysql> Select LENGTH(X''); +-------------+ | LENGTH(X'') | +-------------+ | 0 | +-------------+ 1 row in set (0.00 sec)
Read MoreHow does MySQL QUOTE() function work with comparison values?
When QUOTE() function used with WHERE clause then the output depends upon the comparison values returned by WHERE clause. Following example will exhibit it −Examplemysql> Select Name, ID, QUOTE(Subject)AS Subject from Student WHERE Subject = 'History'; +-------+------+-----------+ | Name | ID | Subject | +-------+------+-----------+ | Aarav | 2 | 'History' | +-------+------+-----------+ 1 row in set (0.00 sec)
Read MoreIn what cases, we cannot use MySQL TRIM() function?
Actually for using MySQL TRIM() function we must have to know the string which we want to trim from the original string. This becomes the major drawback of TRIM() in the cases where we want to trim the strings having different values. For example, suppose we want to get the output after trimming the last two characters from the strings but every string is having different characters at last two places.Examplemysql> Select * from Employee; +------+----------------+------------+-----------------+ | Id | Name | Address | Department | +------+----------------+------------+-----------------+ | 100 | Raman ...
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