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Database Articles
Page 266 of 547
How can group functions be used in ORDER BY clause?
We can sort the result set groups by using group functions in the ORDER BY clause. By default, the sort order is ascending but we can reverse it by using DESC keyword.Examplemysql> Select designation, YEAR(Doj), count(*) from employees GROUP BY designation, YEAR(DoJ) ORDER BY Count(*) DESC; +-------------+-----------+----------+ | designation | YEAR(Doj) | count(*) | +-------------+-----------+----------+ | Prof | 2009 | 2 | | Asst.Prof | 2015 | ...
Read MoreWhat are recursive stored procedures and why MySQL limits the recursion?
A stored procedure is called recursive if it calls itself. Basically, this concept is called recursion. MySQL limits the recursion so the errors will be less rigorous. We can check this limit with the help of the following query −mysql> Show variables LIKE '%recur%'; +------------------------+-------+ | Variable_name | Value | +------------------------+-------+ | max_sp_recursion_depth | 0 | +------------------------+-------+ 1 row in set (0.01 sec)We can change this value up to 255 with the help of the following query −mysql> SET @@GLOBAL.max_sp_recursion_depth = 255// Query OK, 0 rows affected (0.00 sec) mysql> Show variables LIKE ...
Read MoreCreate a MySQL stored procedure which fetches the rows from a table by using a cursor?
Following is a stored procedure which fetches the records from name column of table ‘student_info’ having the following data −mysql> Select * from Student_info; +-----+---------+------------+------------+ | id | Name | Address | Subject | +-----+---------+------------+------------+ | 101 | YashPal | Amritsar | History | | 105 | Gaurav | Chandigarh | Literature | | 125 | Raman | Shimla | Computers | | 127 | Ram | Jhansi | ...
Read MoreWhat MySQL MAKE_SET() function returns if there are all NULL at the place of strings?
MySQL MAKE_SET() function will return nothing if there are all NULL at the place of strings. Following example will demonstrate it −Examplemysql> Select MAKE_SET(2, NULL,NULL,NULL); +-----------------------------+ | MAKE_SET(2, NULL,NULL,NULL) | +-----------------------------+ | | +-----------------------------+ 1 row in set (0.00 sec)
Read MoreWhat are the most significant differences between MySQL functions and procedures?
The most significant difference between procedures and functions is that they are invoked differently and for different purposes. Other than that following are the differences between procedure and functions −A procedure does not return a value. Instead, it is invoked with a CALL statement to perform an operation such as modifying a table or processing retrieved records.On the other hand, a function is invoked within an expression and returns a single value directly to the caller to be used in the expression. That is, a function is used in expressions the same way as a constant, a built-in function, or ...
Read MoreHow can I return the values of columns from MySQL table as a set of values?
With the help of MySQL MAKE_SET() function, we can return the values of columns from MySQL table as a set of values. To understand it, we are taking the example of Student_Name table which has the following data −mysql> Select * from Student_Name; +---------+-------+---------+ | FName | Mname | Lname | +---------+-------+---------+ | Rahul | NULL | Singh | | Gaurav | Kumar | NULL | | Harshit | NULL | Khurana | | Yash | Pal | Sharma | ...
Read MoreMySQL BIT_LENGTH() function is multi-byte safe or not?
Just like LENGTH() function, MySQL BIT_LENGTH() function is not a multi-byte safe function. As we know that the difference of the result between multi-byte safe functions, like CHAR_LENGTH() or CHARACTER_LENGTH(), and BIT_LENGTH() function especially relevant for Unicode, in which most of the characters are encoded in two bytes or relevant for UTF-8 where the number of bytes varies. It is demonstrated in the example below −Examplemysql> Select BIT_LENGTH('tutorialspoint'); +------------------------------+ | BIT_LENGTH('tutorialspoint') | +------------------------------+ | 112 ...
Read MoreHow can we update MySQL table after padding a string with the values of the column?
We can update MySQL table after padding a string with the values of a column by using LPAD() or RPAD() function along with UPDATE clause. Following the example from ‘examination_btech’ table will make it clearer −ExampleSuppose if we want to append the values, in last, of column course with the string ‘(CSE)’ 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 = RPAD(Course, 11, '(CSE)'); Query OK, 10 rows affected (0.16 sec) mysql> Select * from examination_btech; +-----------+----------+-------------+ | RollNo | Name ...
Read MoreHow can we use prepared statements in a stored procedure?
If we want to use prepared statements in a stored procedure then it must be written inside the BEGIN and END block. To understand it, we are creating an example with the help of which we can get all the records from a table by passing the name of the table as a parameter of the stored procedure.Examplemysql> DELIMITER // mysql> Create procedure tbl_detail(tab_name Varchar(40)) -> BEGIN -> SET @A:= CONCAT('Select * from', ' ', tab_name); -> Prepare stmt FROM @A; -> EXECUTE stmt; -> END // Query OK, 0 ...
Read MoreHow can we overcome the property of CONCAT() function that it returns NULL if any one of the argument is NULL, especially when we want to concatenate the values from the column and any of the columns have NULL as its value?
Problem Statement How can we overcome the property of CONCAT() function that it returns NULL if any one of the argument is NULL, especially when we want to concatenate the values from the column and any of the columns have NULL as its value? The above-said property is not useful especially in the case when we want to concatenate the values from the column and any of the columns have NULL as its value. To overcome this, we can use IFNULL() function along with CONCAT() function. To ...
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