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SEARCH KEYWORD -- SQL Express

  Introducing LocalDB, an improved SQL Express

Updated 2011-11-28: Added reference to the walkthrough of using LocalDB in Visual Studio 2010 and to the new LocalDB Installer. Updated 2011-11-02: Added reference to .NET Framework 4 support for LocalDB in the Q&A section. Introduction It gives me great pleasure to introduce a new version of SQL Express called SQL Express LocalDB. LocalDB is created specifically for developers. It is very easy to install and requires no management, yet it offers the same T-SQL language, programming surfac...

   LocalDB,Microsoft,SQL Express     2012-03-31 00:13:43

  Select top 3 values from each group in a table with SQL

Yesterday, my friend Liu Bing asked me a question about how to select top 3 values for each person in a database table using SQL. I think this question is interesting and it deserves some thoughts. Here I record down how to solve this issue. Assume we have a table which has two columns, one column contains the names of some people and the other column contains some values related to each person. One person can have more than one value. Each value has a numeric type. The question is we want to se...

   SQL,Correlated query,top 3     2013-05-23 03:21:25

  Never ever touch a programmer

This is a technical license plate block example. We don't know whether it is working or not, however, the idea is very good. When you drive through some of the junctions, the camera captures the license number and convert it into text with OCR, and then insert them into the database. Therefore, this license plate on the car becomes a SQL injection. This picture tells us -- never trust user input.Author : 陈皓 Source : http://coolshell.cn/articles/6639.html#more-6639...

   Programmer,SQL injection     2012-04-21 01:19:48

  <=> 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

  Solve Hibernate "Too many connections" issue in MySQL

When working with Hibernate and MySQL, sometimes some exceptions will be thrown after sometime. The exception may seem like : java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections" This means there are too many active connections on the MySQL, you can use SHOW STATUS LIKE '%Threads_connected%'; to check the active connections to MySQL. If you want to change the maximum connections allowed to MySQL. You can execute: set global max_co...

   MySQL,Hibernate,Clos     2013-09-04 22:20:49

  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

  Oracle database to execute multiple statements at command line

Oracle database is now a mature and popular RDBMS which is used by lots of enterprises. With its evolution, many utilities and applications are developed around it as well. Now Oracle database also provides cloud support. As a DBA, managing Oracle database is daily routine work and some tools may be used frequently. One of them is sqlplus, the command line tool for executing SQL command. sqlplus is installed while the Oracle database is installed. To start sqlplus, one just needs to open a termi...

   ORACLE,ORACLE DATABASE,SQLPLUS     2016-12-09 20:11:28

  What is blocking and how would you troubleshoot it?

Blocking is a common occurrence in an SQL server context, but if you are new to the world of database management you might not know what this issue entails and perhaps even fear that it is a sign of serious underlying problems. To allay your fears and clear up the mystery, here is a brief overview of blocking and the steps you can take to tackle it. Image Source: Pixabay SQL blocking explained SQL blocking according to SentryOne is an offshoot of the way that concurrent databases operate. Becau...

   SQL,DEADLOCK     2020-09-17 08:50:55

  Application vs Database Programming

A few years ago, I had a problem.  A database routine for processing bulk payments for LedgerSMB that was humming along in my test cases was failing when tested under load with real data prior to implementation.  Some testing showed that while it ran fine with small numbers of inputs, it eventually slowed way down as the number of inputs rose.  Andrew Sullivan, who was also on the project through a different company, suggested it was something called a "cache miss" because I...

   Application Programming,Database programming,Comparison,Difference     2012-03-04 12:08:35

  Fix 'this authentication plugin is not supported' issue while using Go to connect MySQL 8

MySQL 8 has changed its default authentication plugin from mysql_native_password to caching_sha2_password to improve its security. However many third party libraries seem act slowly to catch up with this change. This causes some compatible issues with their connection to MySQL. One of the issues is seen in Go libraries while it's trying to connect to MySQL 8. The specific error has been observed is "this authentication plugin is not supported". The root cause of this issue is that the go-sq...

   MYSQL,GO,MYSQL 8,AUTHENTICATION PLUGIN     2018-07-11 08:55:02

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