MySQL UPDATE Query

There may be a requirement where existing data in a MySQL table need to be modified. You can do so by using SQL UPDATE command. This will modify any field value of any MySQL table.

Syntax:

Here is generic SQL syntax of UPDATE command to modify data into MySQL table:

UPDATE table_name SET field1=new-value1, field2=new-value2
[WHERE Clause]

• You can update one or more field all together.

• You can specify any condition using WHERE clause.

• You can update values in a single table at a time.

The WHERE clause is very when you want to update selected rows in a table.

Updating Data from Command Prompt:

This will use SQL UPDATE command with WHERE clause to update selected data into MySQL table tutorials_tbl

Example:

Following example will update tutorial_title field for a record having tutorial_id as 3.

root@host# mysql -u root -p password;
Enter password:*******
mysql> use TUTORIALS;
Database changed
mysql> UPDATE tutorials_tbl 
    -> SET tutorial_title='Learning JAVA' 
    -> WHERE tutorial_id=3;
Query OK, 1 row affected (0.04 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql>

Updating Data Using PHP Script:

You can use SQL UPDATE command with or without WHERE CLAUSE into PHP function mysql_query(). This function will execute SQL command in similar way it is executed at mysql> prompt.

Example:

Try out following example to update tutorial_title field for a record having tutorial_id as 3.

<?php
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
  die('Could not connect: ' . mysql_error());
}
$sql = 'UPDATE tutorials_tbl
        SET tutorial_title="Learning JAVA"
        WHERE tutorial_id=3';

mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
  die('Could not update data: ' . mysql_error());
}
echo "Updated data successfully\n";
mysql_close($conn);
?>