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Database Articles
Page 546 of 547
How can I search data from MySQL table based on similar sound values?
With the help of SOUNDS LIKE operator, MySQL search the similar sound values from the table. Syntax Expression1 SOUNDS LIKE Expression2 Here, both Expression1 and Expression2 will be compared based on their English pronunciation of sound. Example Following is an example from ‘student’ table which will match the two expressions based on the pronunciation of sound mysql> Select Id, Name, Address, Subject from student where name sounds like 'hrst'; +------+---------+---------+----------+ | Id | Name | Address | Subject | +------+---------+---------+----------+ | 15 | Harshit | Delhi | Commerce | +------+---------+---------+----------+ 1 row in set (0.00 sec)
Read MoreWhat is the use of FLUSH PRIVILEGES statement in MySQL?
Actually, we need to perform flush-privileges operation to tell the server to reload the grant tables. This can be done by issuing FLUSH PRIVILEGES statement or by executing a mysqladmin flush-privileges or mysqladmin reload command. FLUSH PRIVILEGES is really needed if we modify the grant tables directly using such as INSERT, UPDATE or DELETE, the changes have no effect on privileges checking until we either restart the server or tell it to reload the tables. But, Privileges assigned through GRANT choice don't want FLUSH PRIVILEGES to take effect - MySQL server cannotice these changes and reload the grant tables instantly. ...
Read MoreHow can I fetch the value of REPLACE() function in the column name of our choice?
For fetching the values of REPLACE() function in our choice column name, we need to use the keyword ‘AS’ with REPLACE() function. Example mysql> Select Name, REPLACE(Name, 'G','S') AS Name_Changed from student Where Subject = 'Computers'; +--------+--------------+ | Name | Name_Changed | +--------+--------------+ | Gaurav | Saurav | | Gaurav | Saurav | +--------+--------------+ 2 rows in set (0.00 sec) The query above will give the result set of REPLACE() function in column name of our choice ‘Name_Changed’ which is given after keyword ‘AS’.
Read MoreHow can I check how much time MySQL query, without printing it on the console, is taking?
To check this we need to have the profiling information which indicates resource usage for the statements executed during the course of the current session. Profiling information can get by SHOW PROFILE and SHOW PROFILES statement. Before running these statements, the profiling session variable must be set to 1 as follows − mysql> set profiling = 1; Query OK, 0 rows affected (0.00 sec) Now if we will run SHOW PROFILES statement then it will display the list of most recent statements sent to the server along with the duration and query id. mysql> show profiles; +----------+------------+--------------------------------------+ ...
Read MoreHow MySQL SUM() function evaluates if the column having NULL values too?
Suppose if we are calculating the sum of the values of a column which also have NULL values then MySQL SUM() function ignores the NULL values and does the sum of the rest of the values. To understand it, consider the following example of table ‘employee’, having following details − mysql> Select * from Employee; +----+--------+--------+ | ID | Name | Salary | +----+--------+--------+ | 1 | Gaurav | 50000 | | 2 | Rahul | 20000 | | 3 | Advik | 25000 | | 4 | ...
Read MoreWhy is it not recommended to use the mixture of quoted as well as unquoted values in MySQL IN() function’s list?
Actually, MySQL has different comparison rules for quoted values such as strings and unquoted values such as numbers. On mixing the quoted and unquoted values in IN() function list may lead to the inconsistent result set. For example, we must not write the query with IN() function like below − Select Salary from employee where ID IN(1,’a’,2,3,’c’) Instead of this the better way to write the above query is as follows − Select Salary from employee where ID IN(‘1’,’a’,’2’,’3’,’c’)
Read MoreHow can I update MySQL table after quoting the values of a column with a single quote?
As we know that with the help of QUOTE() function we can put the values of a column in single quotes. By using QUOTE() function with UPDATE clause we can update the table having quoted values. We need to give column name as the parameter of QUOTE() function. Following example will update the table ‘examination_btech’ after putting the values of column ‘Course’ in single quotes. Example mysql> UPDATE examination_btech SET Course = QUOTE(Course); Query OK, 10 rows affected (0.05 sec) mysql> Select * from examination_btech; +--------+----------+----------+ | RollNo | Name | Course ...
Read MoreHow changes, made in the current transaction, can be permanently eliminated from MySQL database?
We can use ROLLBACK command to eliminate the changes, made in a current transaction, permanently from MySQL database. Suppose if we run some DML statements and it updates some data objects, then ROLLBACK command will eliminate these updates permanently from the database. Example Suppose we have the following data in table ‘marks’ and we applied the transaction and ROLLBACK command as follows − mysql> SELECT * FROM Marks; +------+---------+---------+-------+ | Id | Name | Subject | Marks | +------+---------+---------+-------+ | 1 | Aarav | Maths | ...
Read MoreHow can we count a number of unique values in a column in MySQL table?
By using DISTINCT keyword along with column name as the argument of COUNT() function we can count the number of unique values in a column. The syntax is as follows − SELECT COUNT(DISTINCT Col_name) FROM table_name; Example Suppose we have the following table mysql> Select * from tender; +----------+--------------+--------------+-------+ | clientid | client_Fname | Client_Lname | value | +----------+--------------+--------------+-------+ | 100 | Mohan | Kumar | 60000 | | 101 | Sohan ...
Read MoreHow OLD and NEW keywords enable us to access columns in row affected by\\na trigger?
As we know that in trigger definition, we can refer to columns of the row being inserted, updated or deleted. Following are the ways OLD and NEW keywords enable us to access columns − We must have to prefix the column name with a qualifier of OLD to refer to a value from the original row. We must have to prefix the column name with a qualifier of NEW to refer to a value in the new row. Now, the use of OLD and NEW must be done appropriately because the triggering event Determines which of them are ...
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