mysql, sql server, oracle, DB2, Access paging technology

mysql, sql server, oracle, DB2, Access paging technology mysql Remember that limit in mysql starts from scratch The main format is as follows: select * from tablename limit m,n For example, look up lines 6 to 20 select * from tablename limit 5,15 The two right-hand writings are equivalent: sel ...

Posted by manjunath on Sat, 15 Dec 2018 12:51:03 -0800

JAVAEE - Mybatis Day 2: Input and Output Mapping, Dynamic sql, Association Query, Mybatis Integration spring, Mybatis Reverse Engineering

1. Learning plan 1. Input Mapping and Output Mapping a) Input parameter mapping b) Return value mapping 2. Dynamic sql a) If tag b) Where label c) Sql fragment d) Foreach tag 3. Association Query a) One-to-one Association b) One-to-many Association 4. Mybatis Integration spring a) How to integrate spring b) Developing dao in a primitive way c) ...

Posted by rodin69 on Fri, 14 Dec 2018 11:00:04 -0800

Dynamic Output (ToB Massive Log Conversion Service) - Aliyun HybridDB for PostgreSQL Best Practice

Label PostgreSQL, UDF, Dynamic Format, Format, JOIN, OSS External Table background Some businesses need to categorize data into dynamic outputs, such as some common log services, where all users'logs are recorded in a unified format, but each end user has different fields of interest, and even different needs for data conversion for each use ...

Posted by LarryK on Fri, 14 Dec 2018 07:18:03 -0800

HTAP database PostgreSQL scenario and performance test 31 - (OLTP) high throughput data in and out (heap, line sweep, no index) - burn after reading (read and write high throughput simultaneous test)

Label PostgreSQL, HTAP, OLTP, OLAP, Scenario and Performance Testing background PostgreSQL is a database with a long history, which can be traced back to 1973. It was first awarded by the 2014 Computer Turing Prize winner and the originator of relational database. Michael_Stonebraker PostgreSQL has similar functions, performance, architectur ...

Posted by i on Thu, 13 Dec 2018 20:06:13 -0800

select_related and prefetch_related for Django query optimization

1. select_related query optimization    select_related obtains all data at one time through multi-table join Association query, and improves performance by reducing the number of database queries, but the association table can not be too many, because the join operation is inherently more performance-consuming. This article ...

Posted by ale_jrb on Thu, 13 Dec 2018 16:27:08 -0800

The Use of MySQL Database-MySQL API Interface in C/C++ Language

MySQL C API migration Porting MySQL header files Makefile Project Visual Studio Project Porting MySQL Library Files Makefile Project Visual Studio Project Add MySQL sample MySQL C API Header file contains Log in to MySQL mysql_initmysql_real_connect Operating MySQL mysql_query Close MySQL mysql_close Read ...

Posted by ruano84 on Wed, 12 Dec 2018 18:09:08 -0800

DB too big? One click helps you shrink all DB file sizes (Shrink Files for All Databases in SQL Server)

This paper introduces a simple SQL script to shrink the size of all non-system DB files in the whole Microsoft SQL Server instance.   As a program ape dealing with SQL every day, it often encounters the situation that DB files are too big and space is full: For developers and testers, if DB data is not particularly important, they will not ...

Posted by bostonmacosx on Wed, 12 Dec 2018 15:06:06 -0800

Java Web Article Management System (Jsp+Ajax+JDBC+MySql Implementation)

This example implements a simple article management system (news management system) using Java Web technology. Its main functions are as follows: User and Administrator Logon Users publish new articles, view details of articles, modify articles, delete and restore articles Users view articles authorized by others and their information Users a ...

Posted by ball420 on Wed, 12 Dec 2018 08:18:06 -0800

Analysis of MySQL process in Waiting for table flush

In a recent case, many queries were blocked and no results were returned. Using show process list, we found that many MySQL threads were in the state of Waiting for table flush. Query statements were blocked all the time and could only be solved by Kill process. Let's take a look at Waiting for table flush's official explanation: https://dev.my ...

Posted by vicky57t on Tue, 11 Dec 2018 19:27:16 -0800

HTAP Database PostgreSQL Scenario and Performance Testing 13 - (OLTP) String Search - Similar Query

Label PostgreSQL, HTAP, OLTP, OLAP, Scenario and Performance Testing background PostgreSQL is a database with a long history, which can be traced back to 1973. It was first awarded by the 2014 Computer Turing Prize winner and the originator of relational database. Michael_Stonebraker PostgreSQL has similar functions, performance, architectur ...

Posted by freejellyfish on Tue, 11 Dec 2018 17:30:08 -0800