Deadlock checking triggered by index_merge

Summary A deadlock problem was sorted out a few days ago. At first, it was puzzled because the two transactions where the deadlock occurred were single-statement transactions with the same type of statement (where attribute columns are the same, but the values are different), and the statements were indexed by the same index, but ultimately a ...

Posted by mb81 on Sun, 07 Apr 2019 16:09:30 -0700

# 1 Database Creation under Android

Under what circumstances do we use databases for data storage? When large amounts of data with the same structure need to be stored. SqliteOpenHelper Create a database step: 1. To create a class integration SqliteOpenHelper, we need to add a constructor to implement two methods, oncreate and onupgrade. Introduction of parameters in the c ...

Posted by MBDesktop on Sun, 07 Apr 2019 13:45:30 -0700

SQL Syntax MySQL Database

SQL statement is a command grammar common to all relational databases, while JDBC API is only a tool to execute SQL statement. JDBC allows the same programming interface to execute SQL statement for different platforms and databases. Basic concepts of relational database and basic commands of MySQL A database is just a place to store user data. ...

Posted by DyslexicDog on Sun, 07 Apr 2019 04:57:32 -0700

Talk about how to program and implement transaction management in Spring

Spring provides the template class org. spring framework. transaction. support. Transaction Template for programmable transaction management, which can meet the needs of some special occasions. Transaction Template is thread-safe, so you can share Transaction Template instances in multiple classes to achieve transaction mana ...

Posted by umer on Sat, 06 Apr 2019 18:57:30 -0700

MySQL Learning Records —— Complex Project Practice

Item 10: Travel and Users (Difficulty: Difficulty) The Trips table contains travel information for all taxis. Each trip has a unique key Id, Client_Id and Driver_Id are the foreign keys of Users_Id in the Users table. Status is an enumeration type with enumeration members ('completed','cancelled_by_driver','cancelled_by_client ...

Posted by Iki on Sat, 06 Apr 2019 15:54:30 -0700

Database Design Report of Supermarket Purchase, Sale and Inventory System

Database Design Report of Supermarket Purchase, Sale and Inventory System Note: This design report omits the requirement analysis section, entity description, contact description, index description, etc. It focuses on the database implementation process, sql language writing and other key presentations that I think are important. In add ...

Posted by russy on Fri, 05 Apr 2019 22:39:30 -0700

Learning Sqlite of Android Together

Summary Android provides completely friendly support for Sqlite, and within the application, any database can be accessed by name. It is recommended to create data tables through subclasses of SQLiteOpenHelpe and override the onCreate() method. This article mainly explains the simple application of Sqlite in Andriod development (add, delete an ...

Posted by duane on Fri, 05 Apr 2019 22:12:30 -0700

4.Mapper.xml Mapping File Details

Important attributes in tags in mybatis: 1. parameterType (input type) First understand: #{} and ${} usage # {} implements setting parameter values to prepareStatement preprocessing statements. In sql statements #{} represents a placeholder, that is?. The use of placeholder {} can effectively prevent sql injection, and mybatis automatical ...

Posted by texelate on Fri, 05 Apr 2019 20:21:30 -0700

On Duplicate Data in MySQL

In sql data processing, it is inevitable to encounter the problem of duplicate data, so how to deal with these duplicate data? Let's see how to deal with it in MYSQL. MySQL handles duplicate data There may be duplicate records in some MySQL tables, and in some cases we allow duplicate data to exist, but sometimes we need to delete th ...

Posted by oeb on Fri, 05 Apr 2019 14:27:31 -0700

Oracle Composite Types: Nested Tables, Variable Arrays and Index Tables

1. Using nested tables and variable arrays in pl/sql 1. Using nested tables in pl/sql Nested tables are used in PL/SQL, where they are equivalent to arrays in other languages. (1) Examples: set SERVEROUTPUT ON DECLARE --The following sentence is nested table declaration TYPE ename_array_type is table of emp.ename%TYPE ; --Define ...

Posted by Fahid on Thu, 04 Apr 2019 10:33:31 -0700