Category: สู่เส้นทางดิจิตอล

When we’re talking communication protocols, a UART, SPI and I2C are the common hardware interfaces people use in microcontroller development.

This article will compare the various interfaces: UART, SPI and I2C and their differences. We will be comparing them with various factors through their protocols, advantages and disadvantages of each interface, etc and we will be providing some examples of how these interfaces are being used in microcontrollers.

Read More

Chrome shows “Translate This Page?” at the translation icon. This may be helpful for first-time users who did not know that that button is there, but showing that every single time is a really stupid design. Users are not idiots; They know that they can press the translation icon if they want translation.

I know I can disable that pop-up in the settings by disabling “Offer to translate pages that aren’t in a language you read”, but then the translation icon is gone from the address bar, and there seems to be no way to use the translation feature. It should be an all-or-nothing feature. For example, I am learning French, so sometimes I want to read the French pages myself (so I do not want the page to be translated), and sometimes I want translation because the page is too difficult.

Read More

Summary: in this tutorial, we will show you how to create an updatable view and update data in the underlying table through the view.

Introduction to MySQL updatable views

In MySQL, views are not only query-able but also updatable. It means that you can use the INSERT or UPDATE statement to insert or update rows of the base table through the updatable view. In addition, you can use DELETE statement to remove rows of the underlying table through the view.

However, to create an updatable view, the SELECT statement that defines the view must not contain any of the following elements:

• Aggregate functions such as MIN, MAX, SUM, AVG, and COUNT.
• DISTINCT
• GROUP BY clause.
• HAVING clause.
• UNION or UNION ALL clause.
• Left join or outer join.
• Subquery in the SELECT clause or in the WHERE clause that refers to the table appeared in the FROM clause.
• Reference to non-updatable view in the FROM clause.
• Reference only to literal values.
• Multiple references to any column of the base table.

Read More

BEGIN TRANSACTION;
INSERT INTO Table2 (<columns>)
SELECT <columns>
FROM Table1
WHERE <condition>;

DELETE FROM Table1
WHERE <condition>;

COMMIT;

In Percona’s managed services, we often receive customer questions on communication failure errors—where customers are faced with intermittent “Got an error reading communication packets” messages. I thought this topic deserved blog post so we can discuss possible reasons for this error, and how to remedy this problem. I hope this will help readers on how to investigate and resolve this problem.

Read More

From the start, FoxPro has always had a wide range of commands and functions for processing text – more than are strictly necessary for a database language. This is a list of some of the more useful commands and functions in Visual FoxPro. Many of them can accept extra optional parameters. Look in the FoxPro Help system for more information.

The distinction between commands and functions is that commands do something whereas functions just return a value to be displayed or used in another command.

Read More

The MySQL server has gone away (error 2006) has two main causes and solutions:

• Server timed out and closed the connection. To fix, check that wait_timeout mysql variable in your my.cnf configuration file is large enough, eg wait_timeout = 28800
• You may also need to increase the innodb_log_file_size mysql variable in your my.cnf configuration to for example innodb_log_file_size = 128MB or higher.
• Server dropped an incorrect or too large packet. If mysqld gets a packet that is too large or incorrect, it assumes that something has gone wrong with the client and closes the connection. To fix, you can increase the maximal packet size limit max_allowed_packet in my.cnf file, eg. set max_allowed_packet = 128M, then restart your MySQL server: sudo /etc/init.d/mysql restart

Once you’ve made these changes, and restarted your MySQL or MariaDB server, the issue should be fixed and no more error triggered. If not, try increase the 128M values to 256M for example. In websites with a lot of traffic and data, you might even need to increase the value to 1024M.

If the above changes do not resolve the issue and if you are using MYSQLI adapter in Matomo, try switching to adapter = PDO\MYSQL in your config/config.ini.php file.

Purpose

Function to commit buffered changes

Syntax

TABLEUPDATE(<expL1> | <expN> [, <expL2> [, <workarea | alias> [, <arrayname>]]])

See Also

Read More