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Database Articles
Page 517 of 547
How to increase varchar size of an existing column in a database without breaking existing data in MySQL?
Increase the varchar size of an existing column in a database with the help of CHANGE command. The syntax is as follows −alter table yourTableName change yourColumnName yourColumnName dataType;Here, we are creating a table with a single column and varchar size 200 −mysql> create table IncreaseVarcharDemo −> ( −> StudentId varchar(200) −> ); Query OK, 0 rows affected (0.60 sec)Now insert record in the table. The query is as follows −mysql> insert into IncreaseVarcharDemo values('John123'); Query OK, 1 row affected (0.16 sec)Displaying all records from the table with the help of the following query −mysql> select *from ...
Read MoreHow to add 30 minutes to datetime in MySQL?
To add minutes to a datetime you can use DATE_ADD() function from MySQL. In PHP, you can use strtotime().To add 30 minutes in MySQL, the DATE_ADD() function is as follows −select date_add(yourColumnName, interval 30 minute) from yourTableName;To use the above syntax, let us create a table. The following is the query to create a table.mysql> create table Add30MinutesDemo −> ( −> YourTime datetime −> ); Query OK, 0 rows affected (0.67 sec)Insert records in the table with the help of following query −mysql> insert into Add30MinutesDemo values(now()); Query OK, 1 row ...
Read MoreDelete more than one rows from a table using id in MySQL?
You can use IN statement to delete more than one rows from a table using id in MySQL. The syntax is as follows −delete from yourTableName where yourColumnName in(value1, value2, .....valueN);To understand the above syntax, let us create a table. The following is the query to create a table.mysql> create table DeleteManyRows −> ( −> Id int, −> Name varchar(200), −> Age int −> ); Query OK, 0 rows affected (3.35 sec)Insert some records in the table with the help of insert command. The query is as follows −mysql> insert into DeleteManyRows values(1, 'John', 23); ...
Read MoreReturning a value even if there is no result in a MySQL query?
You can use IFNULL() function from MySQL to return a value even if there is not result. Let us create a table. Te query to create a table.mysql> create table IfNullDemo −> ( −> Id int, −> Name varchar(100) −> ); Query OK, 0 rows affected (0.60 sec)Insert some records in the table with the help of insert command. The query is as follows −mysql> insert into IfNullDemo values(1, 'John'); Query OK, 1 row affected (0.18 sec) mysql> insert into IfNullDemo values(200, 'Sam'); Query OK, 1 row affected (0.21 sec) mysql> insert into IfNullDemo ...
Read MoreDelete all the records from a MySQL table?
To delete all the records from a MySQL table, you can use the TRUNCATE statement.The syntax is as follows −TRUNCATE TABLE yourTableName;The above syntax deletes all the records from the table. To understand the above syntax, let us create a table. The following is the query to create a table −mysql> create table DeleteAllFromTable −> ( −> PersonId int, −> PersonName varchar(200) −> ); Query OK, 0 rows affected (0.67 sec)Insert some records in the table with the help of insert command.The query is as follows −mysql> insert ...
Read MoreMYSQL select DISTINCT values from two columns?
To select distinct values in two columns, you can use least() and greatest() function from MySQL.Let us create a table with two columns −mysql> create table SelectDistinctTwoColumns −> ( −> StudentId int, −> EmployeeId int −> ); Query OK, 0 rows affected (0.60 sec)Now you can insert records in the table. The query to insert records is as follows −mysql> insert into SelectDistinctTwoColumns values(100, 101); Query OK, 1 row affected (0.39 sec) mysql> insert into SelectDistinctTwoColumns values(102, 103); Query OK, 1 row affected (0.13 sec) mysql> insert into SelectDistinctTwoColumns values(104, 105); Query OK, 1 ...
Read MoreCan we use str_replace in MySQL?
The str_replace version in MySQL is the replace() function. Let us first create a table to understand the function −mysql> create table StringReplaceDemo −> ( −> Id int, −> URL varchar(200) −> ); Query OK, 0 rows affected (0.38 sec)Insert some records in the table with the help of insert command. The query is as follows −mysql> insert into StringReplaceDemo values(1001, 'https://www.google.co.in'); Query OK, 1 row affected (0.09 sec) mysql> insert into StringReplaceDemo values(1002, 'https://www.facebook.com'); Query OK, 1 row affected (0.11 sec) mysql> insert into StringReplaceDemo ...
Read MoreOrder strings by length of characters IN mYsql?
You can order by length of characters with the help of CHAR_LENGTH() function from MySQL. The function returns the number of characters i.e. 4 for the following string −AMITTo order strings by length of characters, the following is the syntax −select *from yourTableName order by CHAR_LENGTH(yourColumnName);To understand the above concept, let us first create a table. The following is the query to create a table −mysql> create table OrderByCharacterLength −> ( −> BookName varchar(200) −> ); Query OK, 0 rows affected (1.97 sec)Insert some records in the table with the help of insert command. The query is ...
Read MoreHow to query between two dates in MySQL?
You can query between dates with the help of BETWEEN statement. The syntax is as follows −select *from yourTableName where yourColumnName between ‘yourStartingDate’ and curdate().Use curdate() or now(), both these functions will work. To understand the above syntax, let us create a table −mysql> create table BetweenDateDemo −> ( −> StartDate datetime −> ); Query OK, 0 rows affected (0.78 sec)Insert some records in the table with the help of the following query −mysql> insert into BetweenDateDemo values(date_add(now(), interval -1 year)); Query OK, 1 row affected (0.11 sec) mysql> insert ...
Read MoreHow to return the nth record from MySQL query?
To get the nth record from MySQL query, you can use LIMIT. The syntax is as follows −select *from yourTableName order by yourColumnName limit n, 1;To understand the above syntax, let us create a table. The following is the query to create a table −mysql> create table NthRecordDemo −> ( −> Id int, −> Name varchar(200) −> ); Query OK, 0 rows affected (0.92 sec)Insert some records in the table using the following query −mysql> insert into NthRecordDemo values(100, 'John'); Query OK, 1 row affected (0.09 sec) ...
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