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MySQLi Articles
Page 90 of 341
While fetching the data as output, how can I use multiple conditions on same column?
Followings are the ways in which we can write a query that returns only records that matches multiple conditions on the same columnBy using ‘OR’ logical operatorAs we know that MySQL ‘OR’ operator compares two expressions and returns TRUE if either of the expression is TRUE. Following example demonstrate that how we can use ‘OR’ operator for multiple conditions on the same columnmysql> Select * from Student WHERE Name = 'Gaurav' OR Name = 'Aarav'; +------+--------+---------+-----------+ | Id | Name | Address | Subject | +------+--------+---------+-----------+ | 1 | Gaurav | Delhi | Computers ...
Read MoreWhy is it not good practice to use date values with two-digits years in MySQL?
As we know that, YEAR(2) stores a year in 2-digit format. For example, we can write 69 to store 1969 as a year. In YEAR (2), the year can be specified from 1970 to 2069 (70 to 69).MySQL interprets 2-digit year values with the help of following rules −Year values in the range 00-69 are converted to 2000-2069. Year values in the range 70-99 are converted to 1970-1999.We must not store date values as a 2-digit format because values stored in this format becomes vague as the century is unknown.It can be understood more clearly with the help of following ...
Read MoreHow can we fetch a particular row as output from a MySQL table?
For fetching a particular row as output, we need to use WHERE clause in the SELECT statement. It is because MySQL returns the row based on the condition parameter given by us after WHERE clause.ExampleSuppose we want to fetch a row which contains the name ‘Aarav’ from student table then it can be done with the help of the following query −mysql> Select * from Student WHERE Name = 'Aarav'; +------+-------+---------+---------+ | Id | Name | Address | Subject | +------+-------+---------+---------+ | 2 | Aarav | Mumbai | History | +------+-------+---------+---------+ 1 row in set (0.00 sec)
Read MoreHow can we use WHERE clause with MySQL INSERT INTO command?
We can use conditional insert i.e. WHERE clause with INSERT INTO command in the case of new row insertion. It can be done with following ways −With the help of dummy tableIn this case, we insert the value from dummy table along with some conditions. The syntax can be as follows −INSERT INTO table_name(column1, column2, column3, …) Select value1, value2, value3, … From dual WHERE [conditional predicate];Examplemysql> Create table testing(id int, item_name varchar(10)); Query OK, 0 rows affected (0.15 sec) mysql> Insert into testing (id, item_name)Select 1, 'Book' From Dual Where 1=1; Query OK, 1 row affected (0.11 sec) ...
Read MoreWhat kind of compound units can be used in MySQL EXTRACT() function?
MySQL EXTRACT() function can use following compound units −SECOND_MICROSECONDMINUTE_MICROSECONDHOUR_MICROSECONDDAY_MICROSECONDMINUTE_SECONDHOUR_SECONDHOUR_MINUTEDAY_SECONDDAY_MINUTEDAY_HOURYEAR_MONTHSome of the examples of these compound units used in EXTRACT() function are as follows −mysql> Select EXTRACT(YEAR_MONTH from '2017-10-20'); +---------------------------------------+ | EXTRACT(YEAR_MONTH from '2017-10-20') | +---------------------------------------+ | 201710 | +---------------------------------------+ 1 row in set (0.00 sec)Above query will return the year and month value from the date.mysql> Select EXTRACT(DAY_HOUR from '2017-10-20 05:46:45'); +----------------------------------------------+ | EXTRACT(DAY_HOUR from '2017-10-20 05:46:45') | +----------------------------------------------+ | ...
Read MoreHow can we add values into the columns of a MySQL table?
INSERT command is used to add values to the columns of a MySQL table. We need to specify the values in INSERT command for all the columns as follows −SyntaxINSERT INTO table_name values(value1, value2, …)ExampleSuppose we have a table named ‘Stock’ with three columns ‘Item_id’, ‘Item_name’ and ‘Item_rate’ then with the help of following query we can add values in these columns.mysql> INSERT INTO Stock values(1, 'HistoryBook', 250); Query OK, 1 row affected (0.07 sec) mysql> INSERT INTO Stock values(2, 'DBMSBook', 280); Query OK, 1 row affected (0.10 sec) mysql> Select * from Stock; +---------+-------------+-----------+ | item_id | ...
Read MoreHow can we automatically define the structure of MySQL table same as the structure of another table?
CREATE TABLE command with LIKE keyword will be able to define the structure of a MySQL table same as the structure of another table.SyntaxCREATE TABLE new_table LIKE old_table;Examplemysql> Create table employee(ID INT PRIMARY KEY NOT NULL AUTO_INCREMENT, NAME VARCHAR(20)); Query OK, 0 rows affected (0.21 sec) mysql> Describe employee; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | ID | int(11) | NO | PRI | NULL | auto_increment | | NAME | varchar(20) | YES | ...
Read MoreHow can I clone/duplicate the table along with its data, trigger and indexes?
For creating a new table just like old one along with its data, trigger, and indexes, we need to run following two queriesCREATE TABLE new_table LIKE old_table; INSERT new_table SELECT * from old_table;Examplemysql> Create table employee(ID INT PRIMARY KEY NOT NULL AUTO_INCREMENT, NAME VARCHAR(20)); Query OK, 0 rows affected (0.21 sec) mysql> Describe employee; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | ID | int(11) | NO | PRI | NULL | auto_increment | | NAME | varchar(20) | ...
Read MoreHow do I generate days from the range of dates in MySQL?
It can be done with the help of following query which uses adddate() function and we are generating the days between ‘2016-12-15’ and ‘2016-12-31’ −mysql> select * from -> (select adddate('1970-01-01', t4*10000 + t3*1000 + t2*100 + t1*10 + t0) gen_date from -> (select 0 t0 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0, -> (select 0 t1 union select 1 union select 2 union select 3 union ...
Read MoreWhat is the significant difference between MySQL TRUNCATE and DROP command?
The most significant difference between MySQL TRUNCATE and DROP command is that TRUNCATE command will not destroy table’s structure but in contrast DROP command will destroy table’s structure too.Examplemysql> Create table testing(id int PRIMARY KEY NOT NULL AUTO_INCREMENT, Name Varchar(20)); Query OK, 0 rows affected (0.24 sec) mysql> Insert into testing(Name) Values('Ram'), ('Mohan'), ('John'); Query OK, 3 rows affected (0.12 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> Select * from testing; +----+-------+ | id | Name | +----+-------+ | 1 | Ram | | 2 | Mohan | | 3 | John | +----+-------+ 3 rows ...
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