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Articles on Trending Technologies
Technical articles with clear explanations and examples
What MySQL ASCII() function returns if I will provide NULL to it?
In this case, the output of ASCII() function depends on the condition that whether we are providing NULL as a string or we are providing simply NULL to it. Following example will demonstrate the difference −mysql> SELECT ASCII(null); +-------------+ | ASCII(null) | +-------------+ | NULL | +-------------+ 1 row in set (0.00 sec) mysql> SELECT ASCII('null'); +---------------+ | ASCII('null') | +---------------+ | 110 | +---------------+ 1 row in set (0.00 sec) mysql> Select ASCII(NULL); +-------------+ | ASCII(NULL) | +-------------+ | NULL | +-------------+ 1 row in set ...
Read MoreHow can we use ASCII() function with MySQL WHERE clause?
While using the ASCII() function with WHERE clause, the output returns by it will depend upon the condition given in WHERE clause. For example, suppose we have a table named ‘Student’ and we want to get the number code, higher than 65, of the first characters of the names of the students. The query for this can be written as follows −mysql> Select * from student; +------+---------+---------+-----------+ | Id | Name | Address | Subject | +------+---------+---------+-----------+ | 1 | Gaurav | Delhi | Computers | | 2 | Aarav | Mumbai | ...
Read MoreHow can we search a record from MySQL table having a date as a value in it?
It can be understood with the help of following example in which we are using the following data from the table named ‘detail_bday’ −mysql> Select * from detail_bday; +----+---------+------------+ | Sr | Name | Birth_Date | +----+---------+------------+ | 1 | Saurabh | 1990-05-12 | | 2 | Raman | 1993-06-11 | | 3 | Gaurav | 1984-01-17 | | 4 | Rahul | 1993-06-11 | +----+---------+------------+ 4 rows in set (0.00 sec)Now, in the following two ways we can search records using the date −mysql> Select * from detail_bday Where Birth_Date = '1993-06-11'; +----+-------+------------+ | Sr | ...
Read MoreHow can we check the default character sets of all the MySQL databases we have on the server?
The query below will return the name of the database along with the default character set −mysql> SELECT SCHEMA_NAME 'Database', default_character_set_name 'charset' FROM information_schema.SCHEMATA; +--------------------+---------+ | Database | Charset | +--------------------+---------+ | information_schema | utf8 | | gaurav | latin1 | | menagerie | latin1 | | mysql | latin1 | | performance_schema | utf8 | | sample | latin1 | | test | latin1 | | tutorial | latin1 | +--------------------+---------+ 8 rows in set (0.00 sec)
Read MoreWhat MySQL returns if specified format string is not as per accordance with the date string passed as arguments to STR_TO_DATE() function?
If the specified format string and date string did not match then MySQL will return NULL value as output along with a warning. Following is an example to understand the same −mysql> Select STR_TO_DATE('20172810', '%Y, %d%m'); +------------------------------------+ | STR_TO_DATE('20172810', '%Y, %d%m') | +------------------------------------+ | NULL | +------------------------------------+ 1 row in set, 1 warning (0.00 sec)The query above returns NULL as output because the format string is having a comma (, ) after %Y but date string is not having any comma after 2017.mysql> Show Warnings\G ...
Read MoreHow can we create a MySQL function to find out the duration of years, months, days, hours, minutes and seconds?
Following is a MySQL function which calculates the duration in years, months, days, hours, minutes and seconds between two dates.mysql> DROP FUNCTION IF EXISTS Duration; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> DROP FUNCTION IF EXISTS Label123; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> DELIMITER // mysql> CREATE FUNCTION Duration( dtd1 datetime, dtd2 datetime ) RETURNS CHAR(128) -> BEGIN -> DECLARE yyr, mon, mmth, dy, ddy, hhr, m1, ssc, t1 BIGINT; -> DECLARE dtmp DATETIME; -> DECLARE t0 TIMESTAMP; -> SET yyr = TIMESTAMPDIFF(YEAR, dtd1, dtd2); ...
Read MoreWhat MySQL returns on passing an invalid string as an argument to STR_TO_DATE() function?
If we pass an invalid string as an argument to STR_TO_DATE() function then MySQL will return NULL as output along with a warning. Following is an example to understand the same −mysql> Select STR_TO_DATE('20173210', '%Y%d%m'); +-----------------------------------+ | STR_TO_DATE('20173210', '%Y%d%m') | +-----------------------------------+ | NULL | +-----------------------------------+ 1 row in set, 1 warning (0.00 sec)In the query above the string value is invalid because of wrong (32) day value. Hence it returns NULL values and a warning which is given below.mysql> Show warnings\G *************************** 1. row *************************** ...
Read MoreHow can we update values in a MySQL table?
With the help of UPDATE statement and WHERE clause, we can update the values in single or multiple rows of the table. MySQL updates the values on the basis of condition specified in WHERE clause. For example, suppose in the ‘employee’ table we want to change the ‘name’ and ‘doj’ of the employee whose id is 1 then it can be done with the following query −mysql> UPDATE employee SET name = 'Gaurav', doj = '2010-02-01' WHERE id = 1; Query OK, 1 row affected (0.06 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> select * from employee ...
Read MoreHow to use MySQL FROM_UNIXTIME() function to return datetime value in numeric format?
As we know that we can convert a time of datetime value to an integer by adding 0(+0) to them. In a similar way, we can convert the datetime value returned by FROM_UNIXTIME() function in numeric format. The following example will clarify it more −mysql> Select FROM_UNIXTIME(1555033470)+0 AS 'Date in Numeric Format'; +------------------------+ | Date in Numeric Format | +------------------------+ | 20190412071430.000000 | +------------------------+ 1 row in set (0.00 sec)After adding 0 (+0) to datetime value MySQL returns the numeric value up to 6 digits microseconds.
Read MoreHow 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 ...
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