index key

In SQL Server, data archiving of super Large tables, using SELECT and Delete commands is very CPU-intensive and disk space, SQL Server must record the corresponding number of transaction logs, and using the switch operation to archive partition

B-tree 1. B-tree Definition B-tree is a balanced multi-path search tree that is useful in file systems. Definition: an m-Level B-tree, an empty tree, or an m-tree that meets the following features:(1) Each node in the tree has at most m Subtrees;(2)

This article is transferred from: Http://www.cnblogs.com/abcdwxc/archive/2007/12/11/990274.html ----------------------- Creates an index for a given table or view.Only the owner of a table or view can create an index for the table. The owner of a

B-tree index access When an oracle process needs to access data blocks in a data file, Oracle has two types of I/O operations: 1) Random Access: Read a data block each time (represented by the "DB file sequential read" Wait event ). 2)

SQL Application and Development: (9) Improving efficiency indexes and SQL Indexes In a database, an index is a special object. It is a database structure that can accelerate data retrieval. It can quickly find the desired content from a large amount

1. Index in SQL Server An index is a disk structure associated with a table or view, which can accelerate the speed of retrieving rows from a table or view. An index contains keys generated by one or more columns in a table or view. These keys are

A preliminary understanding of Oracle B-tree indexes Today, we will study Oracle's B-tree indexes. Through this article, you will know which types of Oracle B-tree indexes are available and how Oracle B-tree indexes are implemented, oracle uses the

MySQL Study Notes summary, mysql Study Notes Slow SQL: A Query whose execution time exceeds the specified time range is called a slow query.In MySQL, how does one record slow SQL statements?A: You can set the following information in my.

B-tree 1. B-tree Definition B-tree is a balanced multi-path search tree that is useful in file systems. Definition: an m-Level B-tree, an empty tree, or an m-tree that meets the following features:(1) Each node in the tree has at most m Subtrees;(2)

So far, our main focus has been onPostfixThe role played at the end of the delivery path. That's it. That is, emails sent to the postfix server are mainly delivered to the local system. However, postfix also plays a role Another role-a repeater

MySQL Study Notes (iii) Performance Optimization 11. MySQL database Locking Mechanism MySQL database locks include table-level locks, row-level locks, and page-level locks. There are four main differences between the InnoDB Storage engine and the

A hash table (hashtable) is also called a "scatter". hashtable is a set of key pairs and value pairs that are organized according to the hash program code of the index key. A hashtable object is composed of buckets that contain elements in a

MySQL performs a full table scan under the following conditions: 1> the data table is too small, and a full table scan is much faster than the search for the index key. This is usually done when the total number of records in a table is less than 10

The application of B + tree in database {Why use B + trees? Concise, because: 1. The file is large and cannot be stored in memory, so it is stored on disk2. The structure of the index minimizes the number of disk I/O accesses during the lookup

what is an index. Indexes are used to quickly look for records with a specific value, and all MySQL indexes are saved as a B-tree. Without an index, MySQL must begin scanning all records of the entire table from the first record until a record is

Lock: Popular speaking is to add lock. Locking is a mechanism that the Microsoft SQL Server database engine uses to synchronize access to the same block of data by multiple users at the same time.Definition: When there are transactional operations,

Depending on the MySQL storage engine, the supported locks are different.Myisam,memory, supports table-level locks.InnoDB, row-level and table-level locks are supported, and row-level locks are the default.Table-level lock to lock the entire table.

MySQL Plus Lock Processing analysis Original: http://hedengcheng.com/?p=7711 background 11.1 Mvcc:snapshot Read vs current Read 21.2 Cluster Index: Clustered Indexes 31.3 2pl:two-phase Locking 31.4 Isolation Level 42 A simple SQL Lock implementation

Original address: http://www.jb51.net/article/36184.htmB-Tree1. B-Tree definitionA B-tree is a balanced, multi-path lookup tree that is useful in a file system.Definition: A B-Tree of M-order, or an empty tree, or a M-fork tree that satisfies the

This article from: Ho Dengcheng's Technical BlogI. BACKGROUNDMysql/innodb's locking analysis has been a difficult topic. In the course of my work, my colleagues have often consulted on this issue. At the same time, the micro-blog also often receive