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Database Articles
Page 244 of 547
How to find the highest number in a column?
You can find the highest number in a column with the help of aggregate function MAX. The syntax is as follows −select max(yourColumnName) as anyVariableName from yourTableName;To understand the above concept, let us create a table with an int column. The following is the query to create a table.mysql> create table HighestNumberDemo −> ( −> BigNumber int −> ); Query OK, 0 rows affected (0.87 sec)Now insert some values in the table. The query to insert records are as follows −mysql> insert into HighestNumberDemo values(1234); Query OK, 1 row affected (0.43 sec) mysql> insert ...
Read MoreMaintaining order in MySQL "IN" query?
You can maintain the order in MySQL IN query with the help of field command. The syntax is as follows −select *from yourTableName anyVariableName where anyVariableName.yourColumnName in(value1, value2, ......N) order by field(anyVariableName.yourColumnName, value1, value2, ......N);To implement the above syntax let us create a table −mysql> create table OrderInDemo −> ( −> Id int, −> Name varchar(100), −> Age int −> ); Query OK, 0 rows affected (1.24 sec)Now let us insert some records in the table. The query to insert records are as follows −mysql> insert into OrderInDemo values(90, ...
Read MoreHow to change Table Engine in MySQL?
You can change table engine with the help of alter command. The syntax is as follows −alter table yourTableName ENGINE = yourEngineName;To understand the above syntax let us create a table with engine MyISAM. Later you can change any other engine. The following is the query to create a table.mysql> create table ChangeEngineTableDemo −> ( −> MovieId int, −> MovieName varchar(100), −> IsPopular bool −> )ENGINE = 'MyISAM'; Query OK, 0 rows affected (0.37 sec)Look at the above query, the table engine is MyISAM, now you can change it to any other engine. Here, we will change ...
Read MoreGet date format DD/MM/YYYY with MySQL Select Query?
Use the STR_TO_DATE() function from MySQL to set a date format for displaying DD/MM/YYYY date. The syntax is as follows −SELECT STR_TO_DATE(yourColumnName, ’%d/%m/%Y) as anyVariableName from yourTableName.To understand the above syntax, let us create a table −mysql> create table DateFormatDemo −> ( −> IssueDate varchar(100) −> ); Query OK, 0 rows affected (0.54 sec)Inserting some string dates into the table. The query to insert date is as follows −mysql> insert into DateFormatDemo values('26/11/2018'); Query OK, 1 row affected (0.14 sec) mysql> insert into DateFormatDemo values('27/11/2018'); Query OK, 1 row affected (0.18 sec) mysql> ...
Read MoreHow to cast DATETIME as a DATE in MySQL?
To cast DATETIME as a DATE in MySQL, use the CAST() function. The syntax is as follows −select cast(yourColumnName as Date) as anyVariableName from yourTableName;To understand the above syntax, let us first create a table −mysql> create table ConvertDatetimeToDate −> ( −> YourDatetime datetime −> ); Query OK, 0 rows affected (0.95 sec)Inserting datetime into the table with the help of insert command. The query is as follows −mysql> insert into ConvertDatetimeToDate values(date_add(now(), interval 1 day)); Query OK, 1 row affected (0.17 sec) mysql> insert into ConvertDatetimeToDate values(date_add(now(), interval -1 day)); Query OK, 1 row affected (0.15 sec) ...
Read MoreCreate a new table with the properties of an old table and without duplicates using MySQL LIKE Operator?
To achieve this with LIKE operator, the following is the syntax −CREATE TABLE yourTableName2 LIKE yourTableName1;To understand the syntax, let us create a table and insert some records into it. The following is the query to create a table −mysql> create table Employee −> ( −> EmployeeId int −> , −> EmployeeName varchar(100) −> ); Query OK, 0 rows affected (0.54 sec)Inserting records into the table with the help of insert command. The query is as follows −mysql> insert into Employee values(1, 'Carol'); Query OK, 1 row affected (0.18 sec) mysql> insert into Employee values(2, 'John'); ...
Read MoreHow can we retrieve file from database using JDBC?
The ResultSet interface provides the methods named getClob() and getCharacterStream() to retrieve Clob datatype, In which the contents of a file are typically stored.These methods accept an integer representing the index of the column (or, a String value representing the name of the column) and retrieves the value at the specified column.The difference is the getClob() method returns a Clob object and the getCgaracterStream() method returns a Reader object which holds the contents of the Clob datatype.ExampleAssume we have created a table named Articles in the database with the following description.+---------+--------------+------+-----+---------+-------+ | Field | Type ...
Read MoreHow can I enable MySQL slow query log without restarting MySQL?
We can enable the MySQL slow query log with the help of SET statement.The following is the syntax.SET GLOBAL slow_query_log = 'Value';In the above syntax, value can be filled with ON/OFF. To enable slow query log, let us see the query.mysql> SET GLOBAL slow_query_log = 'ON'; Query OK, 0 rows affected (0.00 sec)To check if the slow query is ON, implement the following query −mysql> SHOW GLOBAL VARIABLES LIKE 'slow\_%'; Here is the output.+---------------------+--------------------------+ | Variable_name | Value | +---------------------+--------------------------+ | slow_launch_time | 2 ...
Read MoreHow to create a MySQL table with InnoDB engine table?
To create a table with InnoDB engine, we can use the ENGINE command. Here is the query to create a table.mysql> create table EmployeeRecords - > ( - > EmpId int, - > EmpName varchar(100), - > EmpAge int, - > EmpSalary float - > )ENGINE=INNODB; Query OK, 0 rows affected (0.46 sec)We have set the ENGINE as INNODB above.Check the full description about the table using the DESC command.mysql> DESC EmployeeRecords;The following is the output.+-----------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+--------------+------+-----+---------+-------+ | EmpId ...
Read MoreMySQL SELECT last few days?
To select last few days, use DATE_ADD() function in MySQL. The syntax is as follows −select date_add(curdate(), interval - anyIntgegerValue day);Or you can DATE_SUB() from MySQL.select date_sub(curdate(), interval anyIntgegerValue day);Or you can use the following syntax −select curdate() - interval anyIntgegerValue day;Here is the example of all syntaxes shown above to select last few days.Case 1 − Use of DATE_ADD() functionThe query is as follows −mysql> select date_add(curdate(), interval -6 day);Here is the output −+-------------------------------------+ | date_add(curdate(), interval -6 day) | +-------------------------------------+ | 2018-11-20 | +-------------------------------------+ 1 row ...
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