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Delete duplicate rows1 DELETE fromecm_member_login_session2 WHERE( Number, Client_code)inch (3 SELECT Number, Client_code fromMall.ecm_member_login_sessionGROUP by Number, Client_code having COUNT(*)> 1) 4 andUpdate_time not inch (5

One, SQL statements1. Operational database(1) Create a databaseCREATE DATABASE [IF not EXISTS] db_name [create_specification [, Create_specification] ...]Create_specification:[DEFAULT]   CHARACTER SET Charset_name | [DEFAULT] COLLATE collation_name~

The database is an IO-intensive application whose primary responsibility is to manage and store the data. And we know that the time to read a database from memory is the microsecond level, while reading an IO from a common hard disk is at the

Transferred from: http://blog.csdn.net/wud_jiyanhui/article/details/7403375What is an indexAn index is a special file that includes reference pointers to all records in the data table. When an update is made to a data table record, the index is

MySQL is an open-source relational database. For those unfamiliar with these terms, a database was where an application keeps it data, and relational refers to how the Data is organized and accessed within the database. SQL refers to the language

Today, database operations are increasingly becoming a performance bottleneck for the entire application, which is especially noticeable for web applications. It's not just about the performance of the database that DBAs need to worry about, it's

Today, database operations are increasingly becoming a performance bottleneck for the entire application, which is especially noticeable for web applications. It's not just about the performance of the database that DBAs need to worry about, it's

The software mentioned below can be downloaded in the following link.You can use the following action to record the video to complete the relevant operation.Use PowerDesigner and pdmreader to reverse generate MySQL data dictionary. Wmv_ free high

The latest project uses the connection pool of C3P0 in Hibernate, and the database is Mysql. There is no problem with the development and testing. An exception occurs during each idle period of time: java code org. hibernate. exception.

When migrating a database from MSSQL to MySQL, You need to insert 0 values in the auto-increment column of MySQL based on the requirements of business logic. In MSSQL, this is done as follows:Copy codeThe Code is as follows:String SQL; SQL = "set

This is the first article in the MySQL database performance optimization topic series: MySQL database performance optimization-Cache parameter optimization database is an IO-intensive application, whose main responsibilities are data management and

Mysql tutorial two Server database tutorial synchronous data backup method 1. Server StatusServer A: 192.168.1.1Server B: 192.168.1.2 2. Create a synchronization userHost Domain A: 192.168.1.2 User Name A: sync_a Password A: aaaHost Domain B: 192.168

Why does the database require ImplictCommit (implicit commit of transactions) First look at an SQL statement. What do you think is the output of the last SQL statement? SET AUTOCOMMIT = 1;BEGIN;INSERT INTO t1 VALUES (1);CREATE TABLE t2 (pk int

MySQL databases are IO-intensive programs. Like other databases, their main functions are data persistence and data management. This article focuses on optimizing MySQL database cache parameters such as query cache, table cache, log cache, index

1. What is read/write splitting?   One of the most powerful functions of MySQL Proxy is to implement Read/Write Splitting )". The basic principle is to allow the primary database to process transactional queries, but to process SELECT queries from

You can set the value of the date. timezone key to 'Asia/Shanghai' in the urban configuration of the PHP script in php. ini. However, the shared VM itself does not have the permission to modify php. ini. This should be added to the public part of

Periodic analysis table ANALYZE [LOCAL | NO_WRITE_TO_BINLOG] TABLE tbl_name [, tbl_name] This statement is used to analyze and store the table's keyword distribution. During the analysis, a read lock is used to lock the table. This applies to MyISAM,

1. What is an index? Indexes are used to quickly search for records with specific values. All MySQL indexes are saved as B-trees. If no index exists, MySQL must scan all the records of the entire table from the first record until the required

MySql database is the first choice for Small and Medium-sized website back-end databases because it is free for non-commercial applications. website developers can build a "Linux + Apache + PHP + MySql" platform, which is the most cost-effective and

1. What is an index? Indexes are used to quickly search for records with specific values. All MySQL indexes are saved as B-trees. If no index exists, MySQL must scan all the records of the entire table from the first record until the required