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  <=> operator in MySQL

Have you ever seen "<=>" in a SQL query while using MySQL? Does it mean less and equals to and greater than? Actually if you consider it as the union of <= and =>, great, you are close to it. This is one form of equal operator in MySQL, it has the similar meaning to the = operator with some subtle difference. According to MySQL documentation, <=> is NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operand...

   MySQL,NULL safe,<=>     2014-03-24 06:23:22

  An example of SQL outer join

SELECT MEMBER.Name, MEMBER.Address, ORGANIZER.phoneNo, TRAVEL.Tour_Name, TRAVEL.Start_Date, TRAVEL.End_Date FROM TRAVEL RIGHT JOIN ((MEMBER LEFT JOIN ORGANIZER ON MEMBER.Member_ID=ORGANIZER.memberID) LEFT JOIN PARTICIPATION ON MEMBER.Member_ID=PARTICIPATION.MemberID) ON TRAVEL.TravelID=PARTICIPATION.TravelID;...

   Access,SQL,Outer join     2011-03-20 09:08:11

  Resolving SVN error "Error validating server certificate for..."

When using SVN to connect secure server, the server needs to send its certificate to the client for verification. In some cases, the certificate sent by the server is not a trusted certificate, the client may choose to trust the certificate if the server is target server for sure.  But users may get "Error validating server certificate for 'https://...'" the next time when they try to connect to the same secure server even if they specified "p" the first time when they are prompted to accep...

   SSL,SVN,SVN.SSL.SERVER     2016-06-27 07:36:49

  Simple PHP paging class

Frequently in our web applications, we may have many records in the database to display. In order to imrpove loading speed and efficiency, we may need to display some records at a time, so we need to paginate the records. For example, if we have 1 million book records and when users want to view the book list, it's inefficient to display all the records on the same page, we may need to have some pagination to allow displaying a portion of the records such as 20 records per page. This is a simple...

   PHP,Paging,Class     2012-09-10 20:23:33

  How to optimize MySQL insert statement

For a big data system, one problem is the data access efficiency, one more problem is that the data insertion is very slow. We had a service system, the data loading process would take 4-5 hours. This time consuming operation is risky since if the program is interrupted during the loading process, it might be rerun, this will be troublesome. So it's necessary to improve the insertion efficiency for big data systems. Here we provide two optimization suggestions. 1. Combine multiple insert stateme...

   MySQL,insert,optimization     2012-10-24 22:03:13

  Removing duplicates in sql

In modern web development, it’s standard practice to make use of a database abstraction layer, typically an Object-Relational Mapper based on either the Active Record pattern or the Data Mapper pattern. There are several pros and cons to this which are fairly well established, so I’ll spare us all from enumerating them all right now. One established pro worth mentioning is that these systems typically provide a high level interface for fetching data, often removing the need to ...

   SQL,Duplicate,Remove,Web design     2012-01-05 08:20:13

  SQL Server: Removing Deprecated Code and Future Proofing your Queries

New features are added with every release of SQL Server and as a result, some features get removed or deprecated. Deprecated features are features that are still operational (for backward compatibility) but will be removed in a future version. Deprecated features can be of two types: those that will be deprecated in a future version and those that will be deprecated in the next version.In this article, we will explore how to track deprecated code and correct it. I will also share our observation...

   SQL Server,Microsoft,MS SOL,Proof query,Remove redundancy     2011-10-17 11:14:49

  Guide on recovering data in MySQL

In our daily work, there might be mistakes made which got some data or even databases deleted in MySQL. If this happens on production, it would be a nightmare. In case this happens, normally DBA would jump in to save the world. And they would try to recover the data from the backup if there is any. But if there is no backup, then the show stops. Hence database backup is necessary on production environments to avoid such awkward situation. Also normally in MySQL, binlog should be enabled as well ...

   MYSQL,DATABASE,BACKUP,BINLOG,EXAMPLE     2020-08-26 07:50:30

  10 notorious computer virus

The history of computer virus is the same as computer history. With more and more powerful computers, virus also are smarter and harder to be detected and killed. They have big impact on data security and system usability. We introduce 10 notorious computer virus in the history. 1. Creeper In 1971, the Creeper virus, an experimental self-replicating program, is written by Bob Thomas at BBN Technologies. Creeper infected DEC PDP-10 computers running the TENEX operating sy...

   Computer virus,History,Security     2013-07-16 21:09:22

  Work with MySQL character set and collation

For non-English websites, they often have to deal with character set and collation if they want to store data to and read data from databases with other languages. Character set tells the database which kind of character encoding scheme to use to store or read data, collation can be simply understood as a subset of character set, it tells the database how to sort data. We talk about working with character set and collation of MySQL today.  In MySQL, if we want to store Chinese, Japanese or ...

   MySQL,character set,collation,Chinese,question mark     2012-06-17 07:07:28

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