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Database Articles
Page 365 of 547
What is the purpose of ORDER BY columnname*1 in MySQL?
MySQL will implicitly convert the column into a number. Following is the syntax −select * from yourTableName order by yourColumnName*1;Let us first create a −mysql> create table DemoTable1441 -> ( -> Id varchar(30) -> ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert −mysql> insert into DemoTable1441 values('301'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable1441 values('23'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable1441 values('345'); Query OK, 1 row affected (0.42 sec) mysql> insert into DemoTable1441 values('10'); Query OK, 1 row affected (0.23 sec) ...
Read MoreHow to set default value to NULL in MySQL?
Use DEFAULT keyword in MySQL to set default value to NULL. Let us first create a −mysql> create table DemoTable1440 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20) DEFAULT NULL, -> StudentAge int DEFAULT NULL -> ); Query OK, 0 rows affected (0.55 sec)Insert some records in the table using insert command. For values left blank, the default gets inserted −mysql> insert into DemoTable1440(StudentName, StudentAge) values('Chris', 21); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1440 values(); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1440(StudentName) ...
Read MoreHow to check if a specific country code exists in a cell with MySQL?
For specific value, use FIND_IN_SET(). Let us first create a −mysql> create table DemoTable1439 -> ( -> CountryId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> CountryCode varchar(20) -> ); Query OK, 0 rows affected (0.49 sec)Insert some records in the table using insert −mysql> insert into DemoTable1439(CountryCode) values('1022_US, 7894_UK'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1439(CountryCode) values('6567_AUS, 7894_UK'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1439(CountryCode) values('6567_AUS'); Query OK, 1 row affected (0.09 sec)Display all records from the table using select −mysql> select * from DemoTable1439;This will produce the ...
Read MoreHow to save JSON array to MySQL database?
For this, you can use JSON data type from MySQL. Let us first create a −mysql> create table DemoTable1438 -> ( -> EmployeeDetails json -> ); Query OK, 0 rows affected (5.97 sec)Insert some records in the table using insert −mysql> insert into DemoTable1438 values('[{"EmployeeId":"EMP-101","EmployeeName":"Chris"},{"EmployeeId":"EMP-102","EmployeeName":"David"},{"EmployeeId":"EMP-103","EmployeeName":"Sam"}]'); Query OK, 1 row affected (0.22 sec)Display all records from the table using select −mysql> select * from DemoTable1438;This will produce the following output −+------------------------------------------------------------------------------------------------------------------------------------------------------------+ | EmployeeDetails | +------------------------------------------------------------------------------------------------------------------------------------------------------------+ | [{"EmployeeId": "EMP-101", "EmployeeName": "Chris"}, {"EmployeeId": "EMP-102", "EmployeeName": "David"}, {"EmployeeId": "EMP-103", "EmployeeName": "Sam"}] | +------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
Read MoreCreate index of three columns in MySQL?
For index, you can use KEY(). Let us first create a −mysql> create table DemoTable1437 -> ( -> StudentId int, -> StudentName varchar(20), -> StudentMarks int, -> StudentAge int -> , -> KEY(StudentId, StudentMarks, StudentAge) -> ); Query OK, 0 rows affected (0.97 sec)Following is the query to check the description of −mysql> desc DemoTable1437;This will produce the following output −+--------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+-------+ | StudentId | int(11) | YES | MUL ...
Read MoreMySQL query to update different fields based on a condition?
Let us first create a −mysql> create table DemoTable1436 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (1.06 sec)Insert some records in the table using insert −mysql> insert into DemoTable1436(Name) values('Chris'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable1436(Name) values('David'); Query OK, 1 row affected (0.40 sec) mysql> insert into DemoTable1436(Name) values('Bob'); Query OK, 1 row affected (0.35 sec) mysql> insert into DemoTable1436(Name) values('David'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable1436(Name) values('David'); Query OK, 1 row affected ...
Read MoreOrder dates in MySQL with the format "01 August 2019"?
To display dates like “01 August 2019”, use ORDER BY STR_TO_DATE(). Let us first create a −mysql> create table DemoTable1435 -> ( -> DueDate varchar(60) -> ); Query OK, 0 rows affected (1.08 sec)Insert some records in the table using insert −mysql> insert into DemoTable1435 values('01 August 2019'); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable1435 values('01 Feb 2018'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1435 values('31 Jan 2017'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable1435 values('01 March 2019'); Query OK, 1 row affected (0.11 sec)Display ...
Read MoreInsert current time minus 1 hour to already inserted date-time records in MYSQL
For subtracting dates, use MySQL DATE_SUB(). Let us first create a −mysql> create table DemoTable1434 -> ( -> ArrivalDatetime datetime -> ); Query OK, 0 rows affected (3.14 sec)Insert some records in the table using insert −mysql> insert into DemoTable1434 values('2019-09-30 21:10:00'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1434 values('2018-09-30 22:20:40'); Query OK, 1 row affected (0.33 sec) mysql> insert into DemoTable1434 values('2017-09-30 23:10:00'); Query OK, 1 row affected (0.19 sec)Display all records from the table using select −mysql> select * from DemoTable1434;This will produce the following output −+---------------------+ | ArrivalDatetime ...
Read MoreFetch specific rows from a MySQL table with duplicate column values (names)?
Let us first create a −mysql> create table DemoTable1431 -> ( -> EmployeeId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> EmployeeName varchar(20), -> EmployeeCountryName varchar(20) -> ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert −mysql> insert into DemoTable1431(EmployeeName, EmployeeCountryName) values('Adam Smith', 'AUS'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1431(EmployeeName, EmployeeCountryName) values('Chris Brown', 'US'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1431(EmployeeName, EmployeeCountryName) values('John Doe', 'UK'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1431(EmployeeName, EmployeeCountryName) values('Chris Brown', 'AUS'); Query ...
Read MoreAppend special characters to column values in MySQL
Let us first create a −mysql> create table DemoTable1626 -> ( -> Name varchar(20) -> ); Query OK, 0 rows affected (0.37 sec)Insert some records in the table using insert −mysql> insert into DemoTable1626 values('Chris'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1626 values('Bob'); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable1626 values('Robert'); Query OK, 1 row affected (0.13 sec)Display all records from the table using select −mysql> select * from DemoTable1626;This will produce the following output −+--------+ | Name | +--------+ | Chris | | Bob | | ...
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